Video
Is Wilderness Dead
Transcript
Karen: Thank you very much, Ellen.
Ellen: Thank you, Karen/Vanna. We can go ahead and go to the subtitle. I have to say that I would never have put 'whither' in a paper title or in the title of a seminar, but this is a deliberate play on a very famous paper that is titled "Stationary is Dead: Whither Hydrology?" and they were making a point that a very common function in hydrology, which is that you can assume that the statistical properties of stream flow are constant through time actually has never have been a valid assumption. The parallel here is that, I think, in many cases the assumption that there is wilderness in the sense of a landscape that humans have never altered, unfortunately or fortunately, doesn't work for most of [inaudible 00:01:09]
My backyard national park is Rocky Mountain National Park. I have worked in the wilderness portion of it, and I can be in very remote areas with no obvious human influence, but one of the things that I've come to understand through time is that there are a lot of invisible but very persistent and important effects, so that is really what I would like to explore in the talk today.
The first four photos on this title slide are obviously very heavily impacted environments, but I want to make the point that things that can look very natural can also be heavily altered. I am guessing that many of you as archeologists are much more aware of that than I am. If we could go to the next slide.
This is Moraine Park in Rocky Mountain National Park. It's one of the iconic landscapes in the park. I couldn't even guess how many millions of photos are taken of it each summer now that, I think, we are one of the third or fourth most-visited parks in the country. It's a beautiful area. You can see some elk grazing in the foreground there along the Big Thompson River. I'm going to come back to this photo at the end of the talk because this is also a portion of the park that has changed very dramatically in the last couple of hundred years, and in the last few decades, and that's not necessarily obvious when you look at this very scenic view. If I could have the next slide ...
To briefly go over the structure of the talk, I am going to introduce the basis for this designation of the Anthropocene. I am guessing most of you are familiar with it, but it's a proposal that we should designate a new, very recent portion of geologic time as the Anthropocene in recognition of the very extensive human alterations of a variety of geologic processes and biological and ecological processes. If we can have the next point, Karen, I am going to go through some conceptual frameworks that people who think about the Anthropocene, or look at ecosystems and landscapes in the Anthropocene, use to guide their thinking.
There is a long list here that I will go through briefly. Down to the next point. Then I will use Rocky Mountain National Park for some examples of this in terms of changes in animal populations, specifically elk and beavers, and how those have influenced river corridors. Also, some changes in forest structure and age distribution and how that influences stream systems, and finally, I think, in most respects, the most invisible effects, for most park visitors, which is atmospheric deposition. That's an issue in a lot of national parks, and it is certainly a very big issue in Rocky Mountain, and it is affecting ecosystems in noticeable ways at this point.
If we go to the next slide ... Sorry, one last thing. Then I will talk about the implications of these human alterations in terms of trying to both understand these landscapes but also to make management decisions or set management goals in national parks or national forests that are under any land management.
If we go to the next slide, that is what many of the areas outside of the parks look like. That is the Denver Metropolitan Area. If we go to the next point, again, providing some support for this idea that humans have extensively altered the ecosystem, there are a lot of criteria that you can look at. Here, if you look at sediment transport, on the one hand, we're putting a lot more sediment into rivers because of changes in land cover. This goes back centuries, or millennia, in some parts of the world, when the native land cover was altered for agriculture, either grazing or crops. On the one hand, we're putting more sediment into the rivers, but on the other hand, there is less sediment reaching the oceans because so much is stored in our reservoirs. There are over 100 billion metric tons of sediment and 1 to 3 billion tons of carbon that are in reservoirs that are around the world.
Go to the next point. A recent estimate is that we appropriate somewhere between a third and a half of global ecosystem production and almost half of the earth's surface is now covered with things that are directly devoted to producing our food, so crops and pastures. The next bullet. Much more than half the earth's land surface is directly influence by humans, and, of course, you could make a reasonable argument that the entire surface is indirectly influenced by us because of things like climate change, acid rain, changes in a variety of precipitation and temperature patterns.
Go to the next point, an illustration of this. If you are not familiar with Jonathan Foley's group at the University of Minnesota, which is where I took this human footprint figure from, they have some very nice graphics, and they have some really wonderful little videos of 1 to 3 minutes long that are very effective in presenting a lot of information in a short period of time, and have some very nice graphics with them. Looking at this human footprint, there are some areas where we haven't done too much, particularly at the higher latitudes in the Northern Hemisphere, to some extent the Amazon Basin, parts of Africa and Australia, but certainly in the temperate latitudes, there has been quite a lot of alteration.
Go to the next slide, an example of that. This is a picture of crop land in the Illinois River Basin. Go to the next point. Humans have really altered the nitrogen cycle as an example. We have altered a lot of other nutrient cycles, but nitrogen in particular we are pumping a lot more into the atmosphere through various forms of fossil fuel combustion, and we are certainly putting a lot onto the earth's surface to grow crops. Go to the next bullet. One result of that is that we are putting more nitrogen into the environment, and we have reduced the ability of river corridors, for example, to process and retain that nitrogen, so much higher nitrogen loads going to coastal and near shore areas in most of the high-income countries, and because of that, eutrophication is now a very severe problem. It's received the most attention in the U.S. in association with the Gulf of Mexico and the Mississippi River System, but there are many other examples around the country.
The next point. Irrigated agriculture has grown enormously with the Green Revolution, and, of course, that means that there is not only a lot of land under cultivation, but there is this very intensive manipulation of the resources involved in making that land as productive as possible.
Next point. Looking at rivers, this is downstream from a dam in Sweden. Sweden has a very high percentage of its rivers that are dammed for hydro power, and they also generate a lot of their electricity this way, but, of course, it really alters the river ecosystem. Go to the next point. A map that was put together by a group led by Christer Nilsson, a Swedish riparian ecologist, looking at the degree to which the world's large river systems are altered by flow regulation. You see a lot of red on this. Those are, of course, the strongly impacted areas. Again, the less impacted areas tend to be portions of the tropics or at very high latitudes in the Northern Hemisphere.
Go to the next one. If we look at the United States as an example, only an estimated 2% of the lengths of rivers are not affected by dams, and that is disproportionately in Alaska. The most unaffected rivers are primarily in Alaska, although there are some very large dams being proposed there as well.
Next slide. I used Colorado as an example. This is a map of the drainage network, and anything, whether it is an ephemeral or a perennial channel, is indicated as a blue line here. More than a decade ago, we had over 141,000 points of diversion in surface water. Go the next point. The red map that just appeared, I don't know how many of you remember the very old TV commercial that showed this is your brain, this is your brain on drugs, so this is our drainage network, and this is our drainage network on flow regulation. Very, very highly regulated, and Colorado is a dry region. It's representative of many other dry regions, but even wet areas of the country and wet areas of the world are now experiencing water scarcity or water shortages because we use water so intensively for consumptive purposes.
If we go to the next one, coming back to Moraine Park again, there is a term that I would guess many of you are familiar with, legacy sediment or legacy effects. It's been used for several years now to refer to anything that is a legacy of human activities. It really became much higher profile a few years ago when there was a very important study that I am citing here is Walter and Merritt (2008), where that showed that mill dams, literally thousands of mill dams on rivers throughout the eastern United States, that was the main source of power until they developed techniques to burn coal, for example, and have steam power. Everybody has forgotten about those dams. They have silted-up completely. They have fallen into disrepair, they are breached, but the sediments that accumulated behind those dams continues to exert a very strong influence on small- to medium-sized rivers throughout the areas where these dams existed, so that is one example of a legacy effect.
The point I am making with this slide is that legacy effects are very widespread even where you can't tell, looking at it. Again, this is Moraine Park, a very beautiful area in Rocky Mountain National Park. This area looked very, very different about three decades ago. From where I was taking the photo, along the Big Thompson River, you wouldn't have been able to see much of the foreground because it would have been a very dense riparian willow thicket. I will come back to that story, but, again, the point here is there is good reason for trying to designate an episode of geologic time as the Anthropocene because we have had all of these effects that we've been going over briefly.
If we go to the next slide, a quick historic overview of Moraine Park. You can see, the upper photo is 1964; the yellow area was indicating flow direction. The area that is shown in tan here ... this photo was taken in autumn ... that is the wide valley bottom that you were seeing in the previous slide, and you can see multiple channels going through there. There is a very complex branching channel network. By 1987, we are down to about two active channels, and today, there is really only one channel left on the north side of the valley, so this is an example of that very recent change. People weren't directly doing anything to cause this change, but our manipulation of wildlife populations basically has resulted in declines in beaver numbers and loss of beaver dams. That has caused the system to change from this complex multiple-branching channel network down to a single channel.
If we go to the next slide, again, coming back to this idea of the Anthropocene, the concept was introduced a little over a decade ago. The proposal is that it designated an epoch when human activities really dominate many surface processes on earth. There has been a lot of acceptance by the scientific community, and I think that everybody agrees that there should be an Anthropocene. What people are discussing now is when it should start because that's not so obvious. You could say that it starts with the beginning of agriculture, or you could say that it starts with the Industrial Revolution. Those events are not exactly the same in time. In different places, agriculture started more than 2,000 years ago. In some places, where I live, it started about 200 years ago, so there is some discussion about when to start the Anthropocene, but I think that everyone agrees that it's a reasonable idea.
Go to the next point. Here, again, it's time transgressive by region. Eventually, this will be settled, and there will be some consensus on the thing to designate it. Next point. Again, some illustrations, and evidence of the idea is really becoming more widespread. The little image in the center is the cover of a journal. It was started by Elsevier a year and a half ago. There are a lot of other journals that publish papers related to the idea of an Anthropocene, but now there is also a journal called Anthropocene.
Can we go to the next slide? Looking into the conceptual framework and some of the ideas that people use in looking at landscapes and ecosystems and trying to understand how humans interact with them, one is the "critical zone," and this, interface, was proposed by geologists. I was at a meeting last week where one of my ecologist colleagues said, "Oh, geomorphologists have just discovered ecology," and the point he was making was that ideas inherent in the critical zone have been around for a long time. That's certainly true. There is huge overlap with ecology, but the definition here comes from a Natural Research Council publication right after the start of the millennium.
They're making the point that the critical zone is everywhere that life exists. It goes up into the atmosphere and down into the sub surface and the ground water. Really, the reason to emphasize the structure is to make the point that I think we're all aware of, although we tend to forget it. You can't address many of the complex issues of understanding or managing the natural environment if you don't cross disciplines.
We'll go to the next images here, and we take a slice out of the earth’s surface. There is air, organism, soil, water, rock. As a geologist, I tend to focus on the water and soil part, but I certainly cannot ignore the organisms. (I just realized -that is not my graphic -but there is a typo in organisms.) Anyway, you can't understand those. They are intricately connected in the soil and water, and strongly influence or interact with each other. On the right is another example on the Critical Zone Exploration Network (CZEN) and some of the questions that we're using to get at these. It's another way of saying natural systems are integrated, and we have to approach them in an integrated fashion if we're going to be very effective at trying to understand and manage.
Go to the next slide. A second very important concept that has gotten a lot of attention in the last couple of years, in particular, is this idea of connectivity. Go to the next point. The basic definition - it's obvious - you're transferring matter or energy between different portions of a landscape or an ecosystem, so you could have physical contact. An example I give there is sediment coming off a hillslope goes directly into a river. Or, you could have longer distance transport between two portions of a landscape that don't have a direct physical connection. Eolian dust refers to windblown dust. Here, in Colorado, we can get windblown dust from the Gobi Desert in China. It goes all the way across the Pacific. In England, now, people are starting to pay more attention to the so-called blood rains. It's a very graphic term, but they are reddish dust from North Africa coming down with precipitation, covering the UK.
The point is, you can have connectivity over very long distances without direct connections. If you go to the next bullet, you can also, of course, have disconnectivity, so natural processes or human alterations that keeps things from moving around. The obvious human example for rivers would be levees or dams that limit, in the case of levees, the lateral connectivity between the channel and flood plain, or, in the case of dams, the longitudinal connectivity between upstream and downstream areas. If we take a more subtle example, say, of a natural process, if you have sediment coming off of a hillslope, it may not go directly into a river channel. It may be stored in alluvial sand for hundreds or thousands of years so that alluvial sand is creating some point of disconnectivity.
What many scientists are trying to do now is quantify and categorize these different forms of connectivity and disconnectivity. If we go to the next point, lots of different forms of this. Biological is any type of organism. It could be plant, fish, aquatic insects, whatever you like. Riverine is any material or organism moving within a river channel network. Hydrologic, that's all the different forms of water, so atmosphere, sub surface as well as surface, sediment, I think, is pretty obvious. Unconsolidated mineral material moving across the landscape. Landscape connectivity, how connected are adjacent ridge tops, or ridge tops and valley bottoms, or different portions of whatever landscape unit you choose. For any of these different forms of connectivity, you can specify how much material or how many organisms are moving over what time period they can do that or how frequently they can do that and how far they can move.
It's not necessarily that easy to quantify some of these characteristics. If I wanted to quantify sediment connectivity within a river basin, for example, I would have to look at where the sediment is being produced, how long it takes to get from that point of production on the hillslope into the river network, how long it takes to get out of the river network, so it becomes complicated, but it is certainly something that is feasible and that people are increasingly doing. If you can understand and quantify some of these different forms of connectivity, then you can get a very important perspective, I think, on human effects because a lot of what we do is really change connectivity. Sometimes we increase it, sometimes we decrease it, but being able to understand how we affect natural levels of connectivity can help in thinking about things like organism dispersal, invasive species, pollutants or contaminant transport, and others that you can probably think of in connection with your work.
If we go to the next slide, it's a little bit of an illustration of that, for different types of connectivity, so very generic landscapes. In this landscape, the white blob is supposed to be a glacier ... I have limited artistic skills ... coming down into a channel, and then that sub surface down below the channel where you've got water that is exchanged between the channel and the ground water, the hyporheic zone. If you go to the next arrow, there is the big large-scale controls on any landscape, the inputs of solar energy and internal energy from below the earth's surface, so tectonism, vulcanism, high rates of heat flow. If we go to the next prompt, the lateral connectivity in this drawing would be matter, here, is water, sediment, organic matter, maybe contaminants moving from the uplands into the river network.
Then the second, the lower, purple arrow, variety of organisms and materials moving back and forth between the channel and the floodplain when there is overbank flow, for example, during floods. If we go to the next form of connectivity, longitudinal, shown here by the light blue arrow, a variety of organisms and materials that move both ... in the case of the organisms, they move up and downstream, and in the case of materials, they are mostly moving downstream. The next one, the orange vertical connectivity between that channel and the atmosphere, you have got emergent aquatic insects, for example, going back into the atmosphere, water evaporating, and, of course, a variety of atmospheric inputs, precipitation or eolian dust. Then the lower orange arrow is indicating exchange between the surface and the sub surface, so aquatic insects going into the substrate below the channel or water going into ground water or coming out of the groundwater into the channel, for example.
If we go to the next one, yeah, I like this epigram from E. M. Forster's Howard's End, "Only connect." Go to the next. This is a nice area on the west side of Rocky Mountain National Park, East Inlet Creek. If we go to the next part of this, hopefully, if you don't already think about landscapes this way, when you see a scene like this, you can think about how is it connected to the greater landscape, where are the inputs of matter and energy coming from and going to. I think that is really critical in both understanding and managing natural systems because, as I am sure you are all very aware, any national park effectively doesn't end at the boundaries. There is things coming in from the atmosphere and from outside the ground transport, and I don't just mean park visitors, and there is things going out, so the influence is going both directions. I sometimes think of Rocky Mountain as a little dot in space, but all of the space around it interacts with it and strongly influences what occurs within that dot.
If we go to the next slide, a third basic component of the conceptual framework is the idea of complexity, and complexity here means that the system doesn't behave in a linear fashion, so if I double the water going into a river, for example, by a big rainstorm, I can't necessarily predict the outcome. I know that there is going to be more discharge, but I can't necessarily get very detailed because there are so many other interactions that affect how that water moves down the river. If I look at a river as an example, the dimensions and physical complexity within that river include the characteristics of the bed, the banks, cross-sectional geometry, and the way the river appears on a map in terms of the river and the floodplain.
If we go to the next, the first photo, the headwater creek in Rocky Mountain National Park, as you go down the channel, it's mostly very steep and full of boulders, but every so often there is channel-spanning log jam. As you see here, that creates a backwater, finer sediment, and organic material is stored there. It's a really nice fish habitat, so that terrestrial input in the form of the wood and the log jam creates a more complex system that has physical variability in it. Another way to think of complexity here would be heterogeneity of physical variability in the system. If we go to the next photo, an example of variability along the channel banks.
I figured I'd better put some photos in, outside of Colorado, so this is a channel in Connecticut. You can see the big root wad of the tree is creating a protrusion into the channel, and there is a little embayment on the side. This was taken at very low flow, so variability in characteristics of banks that are associated vegetation or some of those big boulders creates something that is more complex than just a straight narrow approximation of an irrigation channel. Go to the next photo, variability at the plant form scale, this is an aerial view of a tributary of the Yukon River in Central Alaska. The main channel has some really nice secondary cutoff meander band . Of course, across that flood plain, there is quite a variety of differences in grain size, soil moisture, time over which that portion of the surface has been stable, so you have got a variety of habitat diversity and biodiversity associated with that.
One of the issues with complexity is understanding how a system responds through time, which is often in a non-linear fashion, but also understanding how these different sources of physical variability create differences in the form and function of the system. The river is used here as an example. If we go to the next slide, some of the implications of typical complexity. On the one hand, if you think of a river as just an irrigation canal, straight, uniform, smooth banks, everything would move down it, very efficiently, very quickly, water, sediment, nutrients. The farther a river deviates from that perfect simple form, the more physically complex it is, the more likely you are to have a abundant habitat, diverse habitat, and some of these other characteristics that I am going to go through one at a time.
Go to the first photo. This is an example of how physical complexity creates habitat abundance and diversity. This is an underwater view on one of these logjams in Rocky Mountain National Park. The white arrow indicates the flow direction. In the foreground, you can see some of the big tan boulders. That is what most of the channel bed looks like. This is immediately upstream of one of these logjams. You can see a little bit of the wood at the left of the photo. At the back there, the big dark mass, is a really huge boulder that protrudes above the water surface. There is water plunging over the top, and the underside of the water surface that looks kind of silvery at the top of this photo is all air bubbles because of that plunging flow.
What you see in the foreground is some finer sediment. There is organic matter here. There is overhead cover, and I was kneeling on the side of the bank, holding the camera under water, so I was very pleased to see a presumably happy trout that I got in the photo that you can see at the back there, using this nice diverse habitat that is created by the physical complexity.
If we go to the next photo, the second point that I've got at the top there is that physical complexity influences sensitivity and resilience. Sensitivity and resilience are terms that are used by ecologists. Sensitivity refers to if you have a physical disturbance, like a flood or a drought or a fire, does the system change, is it sensitive, and does it change in response to that. Resilience refers to how quickly it recovers. A sensitive system would change in response to a disturbance, but a resilient system would recover and return to its original condition more quickly. The pair of photos that I've got here, they are both what are referred to as beaver meadows, so they are wet valley bottom complexes that are created and maintained by beaver dams.
The upper one is an active beaver meadow along North St. Vrain Creek in Rocky Mountain National Park, and you can see ... again, this is an autumn photo so the valley bottom is tan-colored, but you can see areas of ponded water. There are multiple channels that branch and rejoin across there. It is a very wet and complex valley bottom compared to the adjacent upland. What you see in the lower photo is the upstream end of Moraine Park, in autumn of 2012. The Fern Lake fire was an illegal camp fire at a place called Fern Lake, which is up Forest Canyon, which you see in the background, and it burned for a long time. It burned into the riparian zone in Moraine Park, and I think that the only reason it was able to do that is that the beavers had been gone for about three decades.
If you remember those earlier photos, when the beavers are gone, the dams fall into disrepair, and as you saw in those earlier photos, you go from a multiple-branching channel network back to a single channel. Typically, the water table drops across the valley bottom, so you go to a drier grassland environment. By losing the physical complexity created by the beaver dams, you've also lost some sensitivity and resilience because the whole valley bottom has dried out, and now it's prone to burn in a scenario like this fire.
The other thing that I think it's interesting to point out about that upper photo of North St. Vrain Creek, as many of you may know, we had really record-setting floods in September of 2013 in this region. I was at the downstream end of that North St. Vrain Creek beaver meadow about two weeks after that flood, standing on the road that is at the park boundary, and I couldn't tell there had been any flood in contrast to the story downstream from the National Park boundary. That beaver meadow was amazing at buffering the effects of the flood. The flood waters spread out through those dense willow thickets, into the ponded water, and there was very little effect, so the sensitivity and resilience here refer to things like fires and floods and how well the physical complexity influences the system's response to those disturbances.
If we go to the next photo ... I'm sorry, I thought I had one more. I am going to stay here, then, for a minute, here, on the photo of the two beaver meadows. The other two points here are retention and conductivity. Retention refers to the ability to at least temporarily store whatever is moving downstream, so water, sediment, nutrients, organic matter. The more physically complex a river network is, the more little storage points or big storage points you've got, so little storage points like eddies along the side or small/large [inaudible 00:29:51] like you saw in the earlier photos. Big storage points, wide valley bottoms and flood plains. If you go to something that is less physically complex and more like an irrigation canal, everything in transport in that stream keeps going.
It doesn't stop along the way, and if it doesn't stop along the way, it's less biologically available. Typically, you've got lower water quality, so there are some pretty important implications of being able to retain material that's in flux down the river. The last one, connectivity, you look at that beaver meadow, and, sure, all the beaver dams are limiting the longitudinal connectivity, they're not preventing it because they are not like the big concrete gravely dams that we build, but they're slowing down the passage of material downstream, but they're dramatically increasing other forms of connectivity. Because there are those obstructions of beaver dams in the channel, you are much more likely to get at least a small amount of overbank flow during high discharge periods, so you get connectivity between the channel and the floodplain.
You also get greater vertical connectivity. Those obstructions within the channel force hyporheic exchange, of water going from the surface into the shallow sub surface, and that is very important for dissolved nutrient load and water temperature and dissolved oxygen. Again, the basic implications of physical complexity create more abundant and diverse habitat, typically increase the resilience of systems, increase their retention and increase at least some forms of connectivity with the adjacent valley bottoms and surrounding landforms.
If we go to the next slide, another aspect of complexity is this potential for nonlinear response. Go to the next point here. It's a long definition, but this is the formal definition. It's not just geomorphology, but other disciplines in science define complex systems this way. You've got many interconnected parts, and together, their interactions create some behavior that you can't easily predict, going into understanding a series of events. What I alluded to earlier, if you get a lot of precipitation, it creates a flood, but exactly how that flood moves down the river network isn't necessarily easily predicted because there are many components along the way that can influence that.
If we go to the next point here, one aspect of this is what is referred to as emergence, so patterns that arise from many simple steps. An example is done in white, a tree falls into a river. One outcome of that is that it creates a logjam. That logjam blocks the channel, forces high flow over the channel banks. Some of that water going across the flood plain erodes pre-existing, slightly lower or less well-stabilized areas, and you end up with this network of branching and rejoining channels that we have been seeing in the beaver meadow, associated with beaver dams. It can be a simple starting point of a tree falling into a channel or a beaver building a small dam, but you end up with this very complex outcome of a much wetter valley bottom with branching and rejoining channels.
Go to the next photo ... excuse me, point. One characteristic of a complex system is that it's nonlinear. You can't easily predict the output from the input. The example I've got in white there, a piece of wood floating down a channel, it should be easy to figure out the physical forces on that, but it's not just the physical forces. It's characteristics such as how many other pieces of wood are floating down that channel or sitting there, anchored to the banks and getting in the way. In many natural systems, it very quickly becomes difficult to predict the outcome with any precision because of these nonlinearities and emergent properties.
Go to the next one, resistance and resilience. Go to the next text point. Again, I mentioned these earlier. Resistance, how quickly does the ... or how much does the system change if there is some external perturbation, and that's flood, fire, debris flow, drought, whatever it may be. The next text point, resilience, if it does change, how quickly does it come back, so a resilient system is one that recovers quickly. Go to the next illustration here, you've seen this already, the North St. Vrain Creek beaver meadow, very resistant and very resilient. Since I have been working up there, we haven't had pestilence, but we’ve had most other things. We had fire, flood and drought, and this is a very resistant and resilient portion of the drainage network because it is so physically complex. It's got a lot of buffering in all of that broad flood plain in those areas of ponded water.
We go through droughts, and the stream flow goes way down in other portions of the network, but this is like a big sponge that you can slowly squeeze during a drought. There is enough water stored in the sub surface that it really maintains a much more constant level of stream flow within the meadow and the points downstream from it. We go to the next slide, again, contrast that with Moraine Park. We lost the physical complexity, lost the beaver dams, and lost a lot of resistance and resilience.
Go to the next slide. How do people come into all of this? The first point here, human perceptions. Many of you may be familiar with this term of shifting baseline. It was first developed by people working on commercial marine fisheries. What they were referring to is that if you look at any particular fish, like cod as a particularly well-studied example, the number of fish caught through time goes down, and the size of the individual fish goes down. The fishery is being depleted because the fish are being caught at a faster level than they can reproduce and grow to a certain size, but many fishermen are not aware of that because it's a gradual change. Their direct perceptions of what they're experiencing are over a shorter time frame than this change is occurring.
The idea of shifting baseline, you can summarize it as whatever you are used to becomes normal. If you have always seen urban environments, for example, then something that's not urban is very far from your idea of normal, and the study that I am studying here is by Ann Chin and others and was a study that I participated in. It showed students in introductory geology, geography and environmental science classes at a variety of universities. Photos of rivers, there were a series of these photos, and for each photo, we asked them to rate the photo on a numerical scale with respect to characteristics like how natural was the river, how aesthetically pleasing was it, how dangerous or hazardous was it, was it in need of restoration. We did this in some other countries as well as in the U.S., and there were three places that stood out. The State of Oregon and the countries of Germany and Sweden.
With those exceptions, everywhere else we did the surveys, the students uniformly rated pictures of wood in rivers as being bad, so rivers that had wood in them were dangerous. They were unnatural; they needed restoration; they were aesthetically not pleasing. That was very striking to those of us who did the survey because it's diametrically opposed to how river scientists think about what ... Both ecologists and geomorphologists like wood in rivers because we think it does a lot of good things, physically and ecologically. One explanation that we came up with, for this very negative public perception of wood, is that most people are not used to seeing wood in rivers even if the river flows through a forest. That reflects the fact that we have been pulling wood out of rivers, very actively, for many decades or, in other parts of the world, for centuries.
Even though the river flows through a forested environment, we’re not used to seeing wood in the channel. Therefore, we have a negative perception of it, and that is one example. Of course, the point is that what people think of as natural, based on their cultural environment or the place they grew up or their personal experience, may or may not have a lot to do with what someone who's, say, a natural scientist and has studied historical change in that system would consider natural.
If we go to the next point of this slide, the other thing that I think is important besides human perception is where you are, on the earth's surface, so I called it geomorphic context here. Process domain is the idea that, if you look at any particular portion of the landscape, say a drainage basin, there will be spatial differentiation within that. If I look at the mountain rivers in Colorado at the upper elevations, they are in an alpine environment, and they get only snowmelt. As you know, downstream, they go into sub-alpine forest and then montane forest. They have the snowmelt, but they also get things like forest fires that generate debris flows. They can have convective storms that generate flash floods. The characteristics of the system change spatially, in the example that I'm using, with elevation.
If you're going to start thinking about human effects and this whole idea of what might be natural, or how things have been altered, you have to understand the spatial and geomorphic context, and certainly the biome that you're in, what are the plants and animals that could be influencing the variety of ecosystem or landscape processes. I have been talking about beavers, as an example.
If we go to the next point on this slide, looking at disturbance regime, I mentioned disturbance regime under process domain. Disturbance of the context is anything that changes the ecosystem or the landscape, changes resource availability, changes configuration, changes populations. The obvious example for a river is a big flood. The two photos that I've got here, the one on the left is a sunset from my backyard in 2012, when we were having a lot of fires in the Front Range. The photo on the right is a tributary coming into North St. Vrain Creek in Rocky Mountain National Park that had a fairly substantial debris flow during the 2013 flood, so in the last couple of years, we have had fire and flood as examples of disturbances.
If we go to the next text point, the disturbance regime is the suite of disturbances that occur in a given environment, the spatial pattern and basically the statistical distribution in terms of magnitude, frequency of occurrences. Understanding those can help a lot, I think, in understanding some of these ideas of resistance and resilience and, again, how human activities might have altered the landscape or the ecosystem. You might be thinking, maybe you alter the template that the disturbances has come into, but, of course, we alter disturbance regimes as well. An example for the fire photo would be fire suppression or controlled burns.
I have been many places in the world where we have strongly altered the fire regime and the disturbance associated with that, and we certainly alter the disturbance regime of many rivers through flow regulation, whether it's dams or diversions or how those disturbances move through the network if you have things like levees, for example, channelization.
Go to the next slide. Looking at process domains a little bit more, to illustrate it. Again, spatial variability in processes, and I have got this little hieroglyphic thing on the right. It's supposed to be a map view of a drainage network. Go to the next point here. Maybe the upper part of that network has avalanches as the primary disturbance. Go to the next point, the middle part, of this network might be strongly influenced by debris flows. Go to the next slide. The lower part might be overbank flooding. One more. Downstream then might be influenced by channel migration. The point is, for this, what could be a fairly small river network, you have different types of disturbances at different frequencies and magnitudes as you move down through the river network. Process domains can help to understand the distribution of those and the implications for characteristics such as resistance, resilience and connectivity.
Go to the next slide. An example of process domains on the Colorado Front Range, this is where this webinar is challenging. I can't see your faces, so I don't know if you're following what I'm saying or not, but I thought I would give a more concrete example in the Colorado Front Range. The three colored blobs there are supposed to be three different process domains within the hypothetical drainage network. Go to the next point. Again, in the upper part of the rivers, here, in Colorado, there are certainly avalanches. Those streams flow year-around. The peak flows in spring and early summer are coming primarily from snowmelt runoff and, as floods go, they're well-behaved. They are easy to predict based on the snow pack and the air temperature, and they don't go that high. They are not catastrophic events.
If we go to the next text point, in the middle part of the basin, things get a bit more complicated. We have a much higher frequency of wildfires as we get down into the montane forest. Those can destabilize those hillslopes and cause debris flows and flash floods. We also have the potential for summer convective storms that can create the very damaging flash floods that are hard to predict at very high magnitude. The tributaries now, as we get to these intermediate levels in the mountain range, some of them, the big ones, flow year-around, but many of them only flow during snowmelt. You are getting into drier conditions.
If we go to the bullet on here, by the time you get beyond the mountain front into the Great Plains, it's very dry. All the tributaries only flow right after precipitation, and they can get some pretty amazing flash floods. Again, the point here is that, in order to understand these river networks, I think, you have to have some idea of where you are in the catchment and how climate and the disturbance regime and human land use have change through time, and how they changed through space within this river network.
If we can go to the next slide, coming back to human perceptions, again. Go to the next point. A big one for many of us is, what is natural? I am following conventions in distinguishing human versus natural. There is a very valid argument that humans, of course, are natural. We are biological organisms, but I think that a lot of people will distinguish human and non-human biological influences on landscapes and ecosystems. If you do that, then you can ask the question, what is natural and how do you figure out what the natural conditions are? There is the three concepts that I've got on here. The first one is this idea of natural range of variability, and that is making the point that, if we didn't exist, if people weren't around, there would still be variability in time and space. Climate varies. You go through different types of biological processes. You have earthquakes, volcanoes, tsunamis. There is plenty of natural disturbances.
One part of understanding a system in the absence of human effects is to understand how much variability there is, through time and space, apart from us. The second part is, okay, how do you figure out what that natural range of variability is, if everything in a region has been altered? One approach is to look for places where you have the least impacted environment and use that environment for what are often referred to as reference conditions. Reference conditions are tricky because, first of all, they're hard to figure out, and, secondly, if you do figure out the reference conditions and the natural range of variability, there is a very important question that you can ask. Does it matter?
I could look at the reference conditions and natural range of variability of the Poudre River, which flows right through the city. The city now is about 150,000 people, but you can argue that we can never go back to what it was like prior to human settlement in the area, or at least not in the foreseeable future, so does it really matter if we know that? I would argue that it does matter. Even if we can't return to a completely natural state, having insight into how the system has worked in the past, and particularly what native biota are adapted to, can be very important in trying to restore some portions of the form or function of that natural system, even if you can't go back to a pristine setting. Of course, understanding the land use history is very important, what has altered the system from a completely natural condition, if it was altered, how has that occurred, when did it occur, and to what degree.
If we go to the next one, it is a pair of photos here from Bluebird Lake. The picture in the lower left ... excuse me, lower right, is what Bluebird looks like today. It's a pretty rigorous hike to get up there. It's right at timberline, and you feel like you've achieved something when you get there, and there is this beautiful lake. It is not obvious that that has been anything other than what it is at present, in terms of appearance, but if you look at that photo in the upper left, there was a dam there until fairly recently. It was only removed in 1982. Many of these very high lakes in Rocky Mountain National Park were dammed before the park was designated in 1915, and those dams are grandfathered in.
Now, if you want to understand reference conditions and natural range of variability for those lake ecosystems, it is going to be pretty important to know that there was a dam there for several decades and think about how that affected and might have affected the system. Again, I think it comes back to the idea that, in many cases, past human activities in land use history are not obvious when you look at a landscape or an ecosystem. We can go to the next slide. Looking at this idea of natural range of variability a little bit more, again, the range of fluctuation through time and space of whatever it is that you're focusing on, it could be stream discharge, channel geometry. If you're looking at a river, it could be vegetation communities. If you are looking at a different environment, whatever process or landscape or ecosystem characteristic is of interest, but you are trying to figure out how much and how that varied prior to human influence.
The illustration I've got here, there is some process on the Y access and time on the X access. If you are looking at this tributary A that, I think, is a good example of reference conditions, and B ... We've got two examples of reference conditions, right? I've got B drawn as a yellow line here, and there is some natural range of variability defined by that fluctuation. The altered tributary looks like it's beyond that natural range of variability, so you might say, oh, this is a candidate for river restoration, but if you go to the next point, if you have another system, like A, you get a different natural range of variability, and that could completely change your interpretation where you might say, oh, the altered tributary is actually within the natural range of variability. The whole idea of using natural range of variability, or reference conditions, as a guideline for management in processing the condition of the natural system is problematic because it depends on how much information you have and how complete that is.
Again, people also argue that reference conditions may not be as important if you can't return to them.
We go to the next slide. If there is no place you can go for reference conditions, the whole system has been heavily altered, there are some other ways to approach this. Go to the next point, sediment regime in rivers. That phrase refers to how much sediment comes into the river, how much goes out, so if you want to manage a river for sediment ... and this is an issue in many rivers now because of human alteration. Either there is too much sediment, or there is not enough sediment. Maybe it's not appropriate or even feasible to restore a completely natural sediment regime, but you could try to manage for a regime that keeps the river from undergoing net change, so whatever the sediment supply is, you adjust the flow regime to redistribute that sediment without creating negative change.
A classic example in the national parks is what is going on now in Grand Canyon. They are doing those high-flow experimental releases primarily to manage sediment, and that sediment is coming in from unregulated tributaries, so they are really trying to redistribute that tributary sediment down the couple of hundred miles, of the main stem river, to create beach habitat and backwater areas for native fish. There are other national parks where there is too much sediment because of flow regulation upstream. Another one that I have worked on is Black Canyon of the Gunnison, in western Colorado. The point is, you might not be able to go back to natural sediment or natural flow regime, but you can focus on bringing those two into a desired balance, to create the desired river conditions.
Go the next point. Another way to approach this is what has been called physical integrity. Some of you may be aware of the definition of ecological integrity, the idea that you can maintain populations of communities within an ecosystem. Physical integrity, in the context of a river, is the idea that you can make active form and process. As I was describing for the Grand Canyon, for example, you don't have a completely natural flow regime, but you manage the flow regime to create desired conditions, such as beach habitat for riparian organisms, native fish and recreational users.
Go to the next one on here, the third one, a miniaturized river. I would imagine you could have miniaturized other things, too, like miniaturized wetland, so maybe you can't manage a full-size river because there is so much consumptive water use, or there is so much urban encroachment, or, in national parks, it might be road or campground encroachment. Can you have a smaller version of it that reproduces some of the same habitat, for example, for fish or for water fowl or riparian vegetation? In some cases, it appears that you can. All of these are alternatives if you either don't know exactly what the natural system was like prior to human alteration, or even if you know, but it's not feasible to return to that.
We can go to the next slide. Coming to the case study portion of this, Rocky Mountain National Park. I wanted to go through three examples, briefly. The first one is elk and beavers. This is a very wet beaver meadow that you're seeing a photo of, in the background. If we go to the first text point, the park region has had censuses of beaver populations that go back to the 1880s, so before it was a national park. We know that the beavers were trapped out in the 1840s. They came back after that very nicely. The beavers were once quite abundant. Going into the 1900s, 1930s, '40s, there were a lot of beavers in the park. There are almost none left now. Where the beavers are present, they create these beaver meadows. The dams create the wet valley bottoms. Once the beavers vanish, for whatever reason, the dams fall into disrepair and revert to that single channel that I talked about already. The water table across the valley bottom drops, so you go into this much drier grassland, and usually that single channel cuts down below the level of the surrounding area, so you have this incised river.
If you have a flood now, all those flood waters are contained within that single channel. They are not spread into multiple channels and ponds, so when you have a disturbance like a flood, you lose some of that buffering effect. The flow goes through pretty quickly. It's very erosive. There is sediment, organic matter and nutrients going with it. There is much less diversity and abundance of wetland habitat when you go to that drier meadow environment, and quite a bit of the carbon, nitrogen and phosphorus stays in transport and goes downstream rather than being stored in the beaver meadow, so that leads to water quality issues downstream.
Go to the next text point here. This is a photo of a place. The proper place name is Upper Beaver Meadows in Rocky Mountain National Park. Again, historically, a lot of beaver were there. There are no beaver now. There is a single channel that is incised below the adjacent meadow. As you can see, the meadow is still wetter than the adjacent upland. This photo was taken in June, but the little clumps of vegetation that you see, midway across the meadow, are the remnants of the riparian willows that were once, a few decades ago, much, much more extensive.
I would guess that many of you are familiar with this story either from Rocky Mountain or from Yellowstone. The short versions is that elk were hunted almost to extinction in the park, and some of the big predators and carnivores, like grizzly bears and wolves, were hunted to extinction back in the 1920s. The elk were reintroduced. I believe they brought them in from Yellowstone, and they have done very well. For the past couple of decades, the Park Service has been trying to limit elk populations. It is not at all popular with the public to have controlled hunts, to shoot them, so if you come to Rocky Mountain National Park, and you see elk walking around with what look like orthopedic collars, those are contraceptive collars that they put on the females, so they are limiting the elk population that way.
I have been told the elk are smart enough that they know, if they go outside the park boundaries, they get shot so they tend not to go outside the park boundaries except in the city of Estes Park where they, I think, enjoy people's flowers and ornamental plantings. The elk numbers have increased a lot. The reason I am mentioning that in connection with the beaver meadows is that the elk and the beaver compete for woody riparian vegetation, so willows, aspens, alders, birch, and the elk will behave more or less like domesticated grazing animals. They will spend a disproportionate amount of their time in the riparian zone, and they graze that very heavily, so they will graze these plants to the ground, and there is basically no food supply for the beavers. The elk don't necessarily kill the willows. The root stock offers, in July, but there is not enough of the above-ground plants to support the beavers, so there are probably other things going on. Ecologists think that there may be other things that are limiting beaver populations, too, but certainly one effect is from the elk competition.
Go to the next slide. There is a lot on this slide, but it is a conceptual model of two alternative states, two ways that valley bottoms can exist. In either configuration, they are very stable and self-sustaining, unless they have a disturbance. If you start on the photo on the left that says Beaver Dam, that is not Rocky Mountain National Park. It's up in Canada, but an example of a beaver dam. If you follow the arrow that goes downward and to the right, again, if you take the beavers out, the dams fall into disrepair. The flood waters are contained within a single channel. More likely, that becomes a fairly erosive environment. The channel cuts down, and you end up with this much drier environment. Ecologists have referred to that as an elk grassland. The photo next to that, in the lower right, is an example of what the channel looks like upland in Rocky National Park. It is incised about two meters below the level of the valley bottom.
If you go back to that point on the left that says beaver dam and follow it up to the right, as long as the beavers are present, they maintain the dams so you have these backwater ponded areas. You have much more overbank flow. That creates this very wet valley bottom that supports the trees that don't otherwise grow much on these river networks and dry regions, like willow, aspen, alder. Multiple channels, that, of course, is a really good habitat for beavers, and they are creating their own food larder by supporting these riparian woody plants that they've keep eating, so they build more dams. There’s more ponds, and, again, you have this very stable, self-maintaining system of a beaver meadow.
Two different alternatives, depending on which way you go. In the case of Rocky Mountain, it's not that we've been hunting and trapping the beavers within the park and creating this transition to elk grasslands. It is that our management of other animals has allowed elk populations to grow large, and it has negatively impacted beaver populations. If we go to the next slide, again, a picture of one of these very wet beaver meadows in the background.
Go to the next text point. Now Park Service and Rocky Mountain is very interested in riparian restoration. It is not as straightforward as taking a pair of happy beavers and dropping them off at that upper beaver meadows area and saying, "Be fruitful, and multiply." There is nothing for them to eat or to build dams with, so, if you are going to restore beavers, you have to start thinking about how to get the whole valley bottom back to a different state that will allow the beavers to survive. They need a food supply. They have to have the ability to disperse to other parts of the river network and, not so much in the national parks, but in other areas outside of the park, people have to be willing to allow them to exist. You may be aware that in many cases beavers are trapped and removed because people don't like ponds. They would prefer to see flowing water, or the ponded water creates other issues. It can flood over roads, for example, or building materials from the beaver dams can be transported downstream and clog culverts.
There are a variety of potential problems, but the point I am making here is that it is not the simple reintroducing the beaver. You really have to manage the whole ecosystem of that valley bottom, and the human community that goes with it.
Go to the next point. Some of the things that the park is using now at Rocky Mountain, they put in grazing exclosures. If you come to visit, for the 100th anniversary, this year, you will see areas where this dry grassland, and then there is a very tall fence, and inside that fence there is quite a different vegetation community. There is a really dense thicket of aspen and willow, and those are grazing exclosures for the elk. Those take time, but that is a very effective way to restore. In some cases, not in Rocky Mountain National Park but elsewhere, people are imitating beavers and creating very small temporary jams that can be used to raise the water table, flood some of the valley bottom land, and allow the willows to regenerate, and then you can reintroduce the beaver. Now, you can approach this empirically where you try things and you see what works, or you can use numerical simulations to predict what's likely to happen, with either of those approaches, ideally, using some type of adaptive management where you are learning from what happens or doesn't happen that you wanted to.
Go to the next slide, a second brief example, forest and instream wood. That line of text going across the center there, a tree falls into the channel. If it's what is called a raft piece where a portion is resting above the high-flow channel, that can create a log jam, and what happens next depends on where you are in the network. If you are in a very ... next section. If you are in a very steep, narrow valley not so much happens. The log jam is typically a transient feature. It blows out during the next high flow. The next point. If you are in a wide, low-gradient valley bottom, you can have the same type of feedback that you do for beaver dams, where you create this overbank flow, multiple channels, a very physically complex area that is quite resistant and resilient.
Here, you might be thinking what does this have to do with human effects and legacy. Our management of forests has very important implications for what the river networks look like. One of the things that we have seen, in looking at the river networks in Rocky Mountain National Park, is that you only get the upper half of this diagram with the persistent multiple channels where you have old growth forest and really big trees that dump a lot of wood into channels. Our past history of fires or timber harvests, before the park was designated, has this very long-term effect on the river network.
Go to the next slide. The last one, I am going to go over really briefly because this is not something that I work in, but I think that it's something very important. The photo of a place called Sky Pond in one of the more remote areas in the park. Go to the next point. My colleague, Jill Barren, at the U.S. Geological Survey, has been working with me for more than 20 years, studying this watershed of Loch Vale, go to the next point, and she and her group have shown some really startling things. You hike up to or Sky Pond, which is above it, again, you feel like you have achieved something.
It's a long strenuous hike, and it seems like you're very remote, but there is a lot of nitrate that is coming in, from atmospheric deposition, into this very remote and pristine-looking region. They have seen, over the last 20 to 30 years, that there are changes occurring. There is increasing acidification of the soils and the water because, if you look at that photo in the background, there is not a lot of soil, and there is not that many plants. They don't have a lot of ability to absorb and store nitrogen. Lowland wet places that have thick soils and lots of vegetation would do better, but that is not what you find in this mountainous catchment.
Go to the next point. There is both wet and dry atmospheric nitrogen deposition that are now causing detectable changes in everything from the species of lichens in the alpine zone and the herbaceous vegetation in the alpine zone, to some of the things that are occurring in the forested portion of the watershed along the streams and lake systems. Go to the next slide. This is Loch Vale itself, a very beautiful, and very frequently visited, part of the park. Go to the next slide. It's interesting. There was a study that came out a couple of years ago, looking at national parks throughout the Western U.S. The western side of Rocky Mountain receives much less of input of nitrogen. These are pounds of nitrogen per acre, per year from the atmosphere, from the eastern side. The eastern side gets the upslope winds from all of the urban areas. There is 4 million people that live at the base of this national park now.
If we go to the next point, a lot of that occurs during winter, right now. When all these people are coming to this region to ski, there is a lot of things coming down from the sky besides snow, and the snow can be redistributed by wind, so you can get these really amazing inputs of nitrogen at very limited areas as the snow is redistributed and then melts. The next point. It comes back to a national park not being isolated in any sense. The great majority of the nitrogen is coming from outside the national park. The other 25% is global increases in terms of how we are altering the nitrogen cycle. A park can't easily do anything about those nitrogen inputs, but you have to consider them in thinking about management strategies and sustaining this environment.
Go to the next point. I think that a key point here, I keep using Rocky Mountain as my example because it's the park I know best, but everything I say about Rocky Mountain is not unique. This particular survey of eight Western national parks, they are all getting something from the atmosphere, even Gates of the Arctic and Noatak, which are in the north central part of Alaska. Geographic proximity or distance doesn't mean that you have a pristine landscape, unfortunately.
Go to the next slide. Citations for this. I do have all the references that I am referring to, at the end of the talk. Go to the next slide. Coming to the last part, the implications here. This is a dry portion of the Western U.S. with irrigated agriculture. Go to the next bullet point. I think that understanding human impacts, and even the impacts that occurred decades or a couple centuries ago and are no longer obvious, has very important implications for understanding what is the natural range of growth, how have we moved away from it. Is it possible to return to it? Understanding wetness conditions. Go to the next point. The big question that comes up, again, is do these matter?
If we change system so much that it is impossible to go back to something truly natural, does it really matter? Go to the next point. I think it does because, again, you understand how the system evolved and adapted, and you understand what the biota are adapted to. You also have an understanding of the potential in that system. If I didn't know that there had been beaver in Moraine Park and I went and looked at it, I would think it was a really pretty, single-thread channel, but because I know that there were beaver there, historically, I think about it differently, and I think about the potential for managing it and for altering that ecosystem, differently than I would otherwise.
The next point on here. I think that there are pretty important implications for understanding what can create and maintain ecosystems' sustainability, and, ultimately, our own sustainability in the natural systems. Go to the next slide, the first bullet point. Many scientists are used to thinking about abrupt change in landscapes or ecosystems. Next point. Another way to think of this, instead of thresholds, you could think of them as tipping points. Malcolm Gladwell has a very famous and interesting book that was published a little over ... about 15 years ago now, on tipping points. The next point. Different ways to think about tipping points in the context of managing natural systems, you could think about exceeding some regulatory level. The TMDL there is Total Maximum Daily Load that is allowable in streams, sediment, for example, or nitrogen inputs. The Q stands for discharge in the river.
Or, you can think about tipping points as at what point do I force the system across a threshold between two equally stable alternates , so at what point do I go from a beaver meadow to an elk grassland, or vice versa. At the longer end of this, you could think about tipping points that limit sustainability. When do you cross a tipping point where a species goes extinct in this national park or this ecosystem? Or, when do we cross a tipping point where we just don't have any more water to pump out of the aquifer to irrigate our crops? Or, you can focus on tipping points: the last one is, what are we willing to tolerate? People have different levels of tolerance. Go to the next point. The first ones on this list are by far the easiest to identify. The last ones are harder because they are moving targets.
Go to the next text point. I think that the idea of tipping points or thresholds can be very useful for understanding and managing natural systems. You can focus on identifying them, predicting when they will be crossed, either for better conditions or worse conditions, and then, depending on whether they are desirable to cross, either preventing that crossing or forcing it. If you are trying to restore riparian areas in Rocky Mountain National Park, you may want to force a crossing back to a beaver meadow, from an elk grassland.
Go to the next slide, the next point. Coming back to a point that Karen made when she introduced me, I personally like natural areas, and I really try to avoid cities, so I like to think that I am in wilderness when I am in some of these remote areas when I do work in Alaska or here, in Colorado, but I am really coming to realize that I think that it is a better assumption to start with that, even if I don't see evidence of human activity or alteration of that landscape or ecosystem, there has been some human alteration.
Go to the next point. I think it is more appropriate, in understanding and managing, to start by assuming that people have done something to this landscape in the past even if I can't see it anymore. One of my favorite paper titles was a paper by some aquatic ecologist. They talked about the ghost of land use past and how they continue to impose strain on insect communities. Go to the next point. It's easy to make that default assumption when you're in the type of environment that is showing up in the background, an urban area, but I think, even in geographically remote areas, where very few or no people live today, you also should start with that assumption. It is really overcoming our own changing baseline, a perception. I very much include myself in that. The next point here. As Karen, again, mentioned in the introduction, I worked all over the place, high latitude, low latitude, intermediate latitude.
There are very few places where I think that this assumption does not apply, where people really have had limited direct impact, and certainly, there is almost no place in the continental United States that I would say that about. Go to the next one, the implications. I know that it's important ... I know that I am preaching to the choir, if you are mostly archeologists, but I think that it's critical to understand that historical context and what humans have done to alter landscapes. I think that's critical for natural scientists who are focusing on ecosystems and landscapes.
Next one, I think, it's also very important to treat people as part of the ecosystem. I have been distinguishing human natural all the way through this talk, but I am very aware that we interact intimately with landscapes and ecosystems, and we have to manage our natural environments with the recognition that humans are a key part of them.
The next point. I think an appropriate way to do this is focus on quantifying those thresholds and quantifying system resilience and the conditions that will create integrity and the ability to have a self-sustaining ecosystem and landscape. Go to the next one. Looking forward, two pictures of very altered landscapes. The next point, I think, we can focus on management that will lead us into pathways that can help to protect or actively restore desired conditions, and that will help predict and quantify how these natural systems will respond to rapidly changing climate and to other forms of human resources. Next one, firstly, I think that being able to apply your understanding and manage natural systems, to some extent in the direction you want, is the best way to test how well we think we know the system operates.
Go to the next one. To conclude by coming back to Moraine Park, again, a very beautiful landscape, but now when I look at it, I think about what it looked like probably 50 years ago when there were lots of beaver dams, lots of ponded areas, dense riparian willow thickets. I still like the elk that I see grazing in the foreground. It's not their fault, of course, that all these changes occurred, but I view the system very differently because of that knowledge of human alteration and of legacy that will continue to affect it.
Next slide. References, and I will quit. Thank you very much.
Ellen Wohl: Ellen?
Karen: Yes. I wanted to make sure that I hadn't muted myself. Thank you very much for that incredibly interesting talk. There are lots of things to think about in your presentation. Do people have questions? I am sure you will think of some as we begin our discussion, but as usual I have some comments that I would like to make. When I was listening to you talk about the conceptual part of your presentation, I was thinking about the draw-down of the dam on the Elwha River. Have you been following that?
Ellen Wohl: Yes, I have. That's really interesting. Of course, there are quite a few dam removals going on across the country, but that's one of the bigger ones. It's a good example of how we're trying to undo legacy effects, and it's not as simple as just taking the dam out because you could actually create a lot of damage if you had pond damage from the dam if you removed it quickly because of all the sediment that is stored upstream. In the case of Elwha, I don't think there is any particular contaminants in that sediments, but in many cases sediment stored behind dams have some pretty nasty materials in it. We've been learning as we've been going in terms of dammed river rules of things to do and not do, and they're doing the notched removal. They're not just taking Elwha dam out. It's a huge dam, and they're gradually notching it, and a lot of your sediment could be released gradually so that it doesn't overwhelm the downstream system.
Karen: Yeah, I think, they're doing it, very, very carefully.
Ellen Wohl: Mm-hmm (affirmative).
Karen: I have a question for you. When you were talking about your example of the elk meadows, or the ... What was it?
Ellen Wohl: Elk grassland?
Karen: Elk grassland versus the beaver meadows, can you hazard a guess as to what the effect of removing beaver from the kind of habitat or other types of habitat, after the fur-trapping era or during the fur-trapping era, might have had on the landscape?
Ellen Wohl: Yeah. I think sometime I should write a book called The Great Drying. Most of what people of European descent have done, throughout the continental U.S., is to dramatically dry the landscape. We drain flood plain wetlands. We remove beavers. We have deliberately drained marshes and wet lands. I think the effect of removing the beavers was to create a lot of elk grasslands in the shorter term. The key thing to remember with the beaver trapping, is that once they trapped an area out, they usually left so the trapping pressure went way down. Fremont came through here in 1842, and he writes of lots of abandoned beaver lodges and dams, and almost no beaver, but by the time they were doing those early population censuses in the late 1870s and 1880s, there were pretty healthy beaver numbers. Once the trapping pressure was removed, they came back, pretty quickly.
Karen: Oh, okay.
Ellen Wohl: The effect would have been analogous to what we see now with the elk grazing, but it was relatively short because they didn't kill every single animal, so the beavers were actually able to eventually recolonize.
Karen: Things are different now in Rocky Mountain National Park, for example. There is much more pressure to remove beavers?
Ellen Wohl: They are not actively removing beaver from the park. It is just that there is very high elk numbers and the elk grazing. In areas outside the national park, there are areas where beavers are actively removed, very effectively, so the populations just can't reestablish, but the net effect of whatever causes the beavers to go away , whether it's hunting, trapping or out-competing by the elk, is to really dry the river corridors and the valley bottoms.
Karen: I don’t know if you have had the opportunity to listen to a TED Talk that talked about the long-term effects of removing and restoring carnivores to these types of environments. Have you had a chance to hear that?
Ellen Wohl: I haven't listened to the TED Talk, but I have seen some of the scientific papers where, when they reintroduced the wolves to Yellowstone, they saw a lot of change in the riparian corridors, including the return of some of the beaver colonies because the elk were ... I think it was mainly that the elk were kept moving rather than that there were big reductions in elk numbers, so they couldn't just spend all their time along the rivers.
Karen: Yes. Those studies are so interesting.
Ellen Wohl: Yeah, actually I just happened to think of this. Since I am speaking to an audience of archeologists, I read a paper last night that a colleague sent me. A couple of archeologists ... this was published in the '80s ... in Britain were making the point that many of the ... let's see if I can get this right. I think they were talking about Mesolithic settlements. They were hypothesizing that people used beaver meadows. These were already places where the big coniferous or deciduous forest was gone, and they would preferentially settle along those areas and use them for grazing and crops. Although the archeologists did make the point that really human inhabitants probably removed the beavers to do that. They were talking about the synergy, basically, between beaver alteration of the landscape and how people used it.
Karen: How interesting. The studies that you have done also have implications for fire regimes as well, don't they?
Ellen Wohl: Yes, definitely, and understanding how fire regimes influences things coming into river networks, so wood, sediment, nutrients coming off the hillslopes after a fire or in the absence of fire.
Karen: That, of course, affects our cultural resources and management of cultural resources.
Ellen Wohl: Mm-hmm (affirmative), yes.
Karen: I really appreciate your taking the time to talk to us. I think that archeologists, because of the nature of our work, we’re often very focused on site archeology, and often we are not very well-educated to be able to consider a big landscape picture and big changes of landscapes.
Ellen Wohl: Oh, I think, we all focus in, narrowly, on what we do. It's good to step back and look at the greater landscape, though, occasionally.
Karen: Yeah, yeah, very important. Do we have any more questions for our speaker today? No? Dr. Wohl, thank you very much for joining us today. This is the end of our speaker series for 2014-2015, and I will be sending out announcements when we have more information about the 2015-2016 speaker series. Thank you all.
Ellen Wohl: Thank you.
Description
Ellen Wohl, 1/22/2014, ArcheoThursday
Duration
2 hours, 57 minutes, 6 seconds
Credit
NPS
Date Created
01/22/2014
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