Global warming may seriously affect our ability to protect the species and habitats that are now encompassed by national parks, forests, wilderness areas, and other nature reserves. Many species in Glacier may be particularly sensitive to climate change; for this reason, and because of Glacier's relatively pristine conditions, the park will likely become an important site for global warming research in the future.

Climate and Biotic Changes of the Past
As indicated by geologic and fossil records the earth's climate has changed repeatedly throughout time. During the Pleistocene (which lasted from approximately 2,000,000 years before present [ybp] until 11,000 ybp) evidence shows that the global climate went through many cycles of cooling and warming, each averaging about 100,000 years in length (perhaps caused by cycles in the earth's orbital pattern) (Broecker 1989). Average temperatures fluctuated up and down about 5°C (9°F) as the earth oscillated through a series of glacial (ice age) and interglacial periods. When the last glacial period (the Wisconsin) peaked about 22,000 ybp, the earth was about 3°C (5.4°F) cooler than it is today. The Wisconsin age glaciers (which carved much of the topography scene in Glacier today) were mostly gone by around 11,000 ybp. The interglacial period (which we are still in) peaked around 5,900 ybp when temperatures averaged about 2°C (3.6°F) warmer than today's.

Where plants live is largely determined by climate and where animals live depends largely on where the plants are. Reflecting climate change (and interrelated processes of plate tectonics and evolutionary speciation), the distribution of plants and animals across the globe has also radically changed over time. During the Mesozoic (approximately 230,000,000-63,000,000 ybp) the broad region of which Glacier is a part was home to, among other things, dinosaurs and giant tree ferns (Horner 1988). During the Cretaceous (late Mesozoic) the dinosaurs disappeared, flowering plants emerged, and the primitive mammals and birds that first appeared during the Jurassic began to spread and diversify. By the Pliocene (13,000,000-2,000,000 ybp) plants and animals appeared that we would recognize as distinctly "modem," while many others became extinct. About 10,000 ybp many mammals that once roamed throughout North America disappeared, including mammoths, camels, horses, giant sloths, and saber-toothed tigers (Stanley 1986).

Fossil records show that climate changes during the Pleistocene caused species distributions to shift both in latitude and in elevation (Brubaker 1988). During several Pleistocene interglacial periods, when temperatures in North America were 2-3°C (3.6-5.4°F) higher than today, species were found several hundreds of kilometers north of their present distributions. Osage oranges and pawpaws grew near Toronto; manatees swam in New Jersey; and tapirs and peccaries foraged in North Carolina (Peters 1989). In Glacier during the Wisconsin glacial period treelimit may have been 1,000 m (over 3,200 ft) lower than it is today (Carrara 1989). As the last major glaciers retreated, lodgepole pines, spruce, alder, willow, and other trees, shrubs, and herbs revegetated the areas that had been scraped bare by ice. By around 11,400 ybp most parts of Glacier were deglaciated and treelimit was 500-700 m (about 1600-2300 ft) below today's. As the climate warmed forests continued expanding upward in elevation until they reached the current treelimit (Carrara 1989).

Present and Future Climate Changes
Today human activities are superimposing a different scale of climate change over the natural cycles that have governed the earth's climate for at least a million years (Abrahamson 1989). We may be causing climate to change more quickly than it ever has in the past and much more quickly than either plants and animals or human social, political, and economic systems can adapt to cope with the change. We are doing this by adding "greenhouse gases" to the earth's atmosphere gases which trap heat as glass does in a greenhouse, and make the earth warmer than it would otherwise be. Carbon dioxide (CO2), the single most important greenhouse gas, is a byproduct of the combustion of fossil fuels and the clearing and burning of forests. Another 20 or so greenhouse gases have been identified, the most important of which are: methane which is produced in flooded fields, rice paddies, the guts of cattle and other animals, landfills, and coal seams; chlorofluorocarbons used in refrigerators, air conditioners, and urethane foams; nitrous oxide released by coal combustion and in the breakdown of agricultural fertilizers; and tropospheric (lower atmosphere) ozone which is photochemically produced from the byproducts of fossil fuel emissions (not to be confused with the naturally occurring stratospheric ozone layer which blocks ultraviolet radiation from the sun) (Abrahamson 1989, Ramanathan 1989).

Earth has a natural greenhouse effect as a result of CO2 and water vapor in the atmosphere. If the atmosphere did not contain these gases, the earth's surface temperature would be 33°C (59°F) lower and life as we know it would be impossible. But human activities beginning with the Industrial Revolution have already increased the level of atmospheric CO2 alone by 30%. An increase of 0.7°C (1.3°F) in average global temperature since 1860 has already been measured; most scientists agree that this is a direct consequence of our addition of greenhouse gases to the atmosphere. Even if we were to drastically reduce emissions of greenhouse gases right now, we are probably already committed to an equilibrium surface warming of at least 1-2.4°C (1.8-4.3°F). At present rates of emissions of greenhouse gases, by the year 2030 we would be committed to a mean global warming of at least 3°C (5.4°F) and maybe as much as 5°C. Over a century from now the earth could be 5-10°C (9-11°F) warmer.

Since the earth's climate fluctuates anyway why should we care about current global warming? First of all an increase in the earth's surface temperature of more than 3°C will take us to climatic extremes that the earth has not experienced in at least a million years (Ramanathan 1989). Second, this human-caused change is occurring about an order of magnitude faster than any climate changes evidenced by the geologic and fossil records. The changes at the end of the last ice age spanned several thousands of years. The changes currently being predicted may happen over the course of only a few centuries, and may not be reversible.

Because our understanding of the highly complex global links between ocean currents, atmospheric patterns, and climate is limited, it is difficult to predict the precise ramifications of global warming for specific regions. However, there is some agreement on the following points (Abrahamson 1989):

1. Global warming could cause accelerated melting of the polar ice caps which would raise sea levels anywhere from 20 cm to 2 m in the next century, thereby inundating ecologically valuable coastal marshes and swamps and economically valuable real estate.
2. Climate change will be amplified at higher latitudes; arctic regions may experience 2-3 times the warming experienced in the tropics.
3. The earth as a whole will be more humid, wetter, but the geographical and seasonal distribution of precipitation will change. Summer soil moisture may be significantly reduced in many of the world's major agricultural regions including the U.S. grain belt, the Canadian prairie provinces, the Ukraine, and northern China. One study predicts that rainfall on the Great Plains may decrease 40% (Peters 1989); a 2°C (3.6°F) temperature increase may cause the water supply in the Missouri River drainage to drop by 64% (Revelle & Waggoner 1989).
4. Extreme weather events heat waves, droughts, hurricanes, tornadoes, thunderstorms will become more frequent.
5. A great deal of rearrangement of plants, species, and ecosystems will occur and many species may become extinct because of global warming, as is discussed below.

Effects of Global Warming on Biological Diversity
Each 1 degree C of global warming will shift temperature zones by about 160 km (100 miles). In the northern hemisphere this means that if the climate warms 3°C species may have to shift northward as much as 500 km (300 miles) in order to find suitable habitat under the new climatic regime. They may also have to shift more than 500 m (over 1600 ft) upward in elevation (when you go up 500 m in elevation, you experience the same 3°C cooling as you would by moving 250 km towards the poles) (Peters 1989).

The ability of species to adapt to climate change will depend largely on their ability to "track" shifting climate by dispersing colonists (Peters 1989). But many species, especially plants, are poor dispersers. For example, fewer than 5% of the light, wind-dispersed seeds of Engelmann spruce travel as much as 200 m downwind from their parent tree, giving the spruce an estimated migration rate of only 1-20 km per century. Even some highly mobile animals may be poor dispersers because their distribution is limited by the distribution of particular plants, or for behavioral reasons. Many species of deer, for instance, have dispersal rates of less than 2 km/year, and many interior forest birds simply will not cross unforested areas of any size. Such species may not be biologically capable of shifting their distributions poleward at the rate necessary several hundred kilometers or more per century to keep up with predicted climate changes.

Even for species that are good dispersers natural or man-made barriers may block their dispersal. Mountains, oceans, deserts, unsuitable soils, agriculture, and urbanization may lie on the path between populations and suitable habitat. As Peters (1989) puts it, "Few animals or plants would be able to cross Los Angeles on the way to the promised land." Even if there aren't barriers, there may not be any suitable habitat to move to; species which depend on alpine or arctic habitats, for example, may literally have nowhere to go (Peters 1989).

Other factors that would decrease the probability of species successfully colonizing new habitats and thereby increase the probability of their extinction (Peters 1989) include:

1. Small population size: smaller populations will send out fewer colonists.
2. Small geographic range: reduces the likelihood that part of the species' range will remain suitable when the climate changes.
3. Living in marginal habitat: populations at the natural limits of their range or that have been pushed into marginal habitat by human activities, will be highly susceptible to climate change

Human-caused habitat destruction puts up barriers to dispersal, reduces population sizes, and confines many species to small, isolated, and sometimes marginal habitat patches. Our activities, therefore, are not only stressing ecosystems by inducing rapid climate change, but may be drastically reducing the likelihood that species will be able to cope with such change. The combination of habitat destruction and climate change may act synergistically to create an even larger extinction crisis than is already expected to occur as a result of human encroachment alone (Peters 1989).

Global Warming and Glacier
Global warming may make a mockery of our attempts in all nature reserves, including Glacier National Park, to preserve natural communities and rare, threatened, and endangered native species. Species may no longer "fit" ecologically in the reserves that were set aside specifically to protect them, while areas which might have supported suitable habitats for them under future climate regimes may already have been converted to farms or shopping malls. Furthermore, as populations shift in response to warming their movements will not necessarily be synchronous. Community compositions will change as species move at different rates and others completely disappear. Within the National Park Service it will be necessary to rethink definitions of such terms as "native" and "exotic" species and "natural" communities and to reconsider the NPS policy of minimal intervention in natural processes (Shelton 1988).

How will global warming affect Glacier? Alpine zones may shrink or be eliminated from the park altogether; Logan Pass, for example, might eventually be forested. Many populations in Glacier are at the limits of their range; the ones at their southern limit will likely be the first to disappear from the park as temperature zones shift northward. Rare plants found only in Glacier may be particularly susceptible to extinction. Fisheries may decline as well, as hydrologic patterns shift. If thunderstorm activity increases, fires may become more common and further shift community and landscape patterns away from what we think of as "normal" for this area. Aesthetic values in Glacier may be affected as well (Shelton 1988). The fifty-odd small glaciers in the park may disappear completely within a matter of decades; on the other hand, they may increase in size if, as some models predict, precipitation increases at northern latitudes (Key & Marnell 1990). Water levels in rivers and lakes may change, and present patterns of landscape diversity which create scenic vistas (see Information Paper 1) may be rearranged and, perhaps, simplified as individual species disappear.

Perhaps many of Glacier's species will be able to survive farther north, in the Banff-Jasper area. Protection of corridors linking the Greater Yellowstone Ecosystem, the Crown of the Continent Ecosystem, and parks in the Canadian Rockies may provide critical avenues for species dispersal.

The same factors that may make species in Glacier vulnerable to climate change also make Glacier a valuable place for researching and monitoring the effects of global warming. Peter Lesica at the University of Montana and Bruce McCune of Oregon State University have already begun monitoring six rare alpine plants which reach the southern limit of their geographic range in Glacier, are short-lived perennials, and should, therefore, be particularly sensitive to climate warming. They have set up and permanently marked transects in the Logan Pass area that will be monitored periodically over the years to test the hypothesis that predicted climate warming will in fact cause contraction and eventual extinction of populations of species at the edge of their range (Lesica and McCune 1987, 1992).

Since 1990 the National Park Service has established a Global Change Research Program to take advantage of the diverse and well-preserved ecosystems offered by the parks. Seventy-eight units of the park system, divided into twenty biogeographic areas, are involved in studies of ecological systems and dynamics, earth system history, biogeochemical dynamics, solid earth processes, and climate and hydrologic systems. These national parks contain portions of representative ecosystems throughout the United States. The program is primarily directed toward ongoing monitoring, field and laboratory research, and modeling in order to determine the influence of global change on populations, the structure and function of ecosystems, and their adaptability.

Glacier National Park is well suited for studies on global climate change for a number of reasons:

1. Glacier effectively represents the northern Rockies of the U.S. and Canada and also has strong similarities to protected mountain reserves on other continents, providing opportunity for comparative studies on a global scale.
2. Glacier includes many different microclimates due to its range of elevations and the effects of the Continental Divide.
3. The park is protected and therefore offers a relatively undisturbed area which will not be developed, conditions appropriate for long-term studies.
4. The park's area is over one million acres. Its size thus minimizes outside influences, yet the area is relatively accessible for study.
5. Glacier's pristine systems are effectively extended by other protected areas around it. Its geography includes five major floristic provinces (see Information Paper 6), producing great diversity of plant species which in turn support diverse animal species.
6. With the convergence of these five areas, many species exist at the limits of their ranges. These plants are very likely to be affected early by climate change--treeline may shift upward, outside plants may extend their ranges into the park, or small populations may experience local extinctions (see Information Paper 4).

Many studies related to global climate change are underway. Development of the Regional Ecosystem Simulation System (RESSys) will permit computer modeling of stream flows, snowpack depth, amount of stored carbon in any forest, and the age and structure of any forest in Glacier National Park. RESSys can then be used to simulate forest response to climate change on a number of levels. RESSys is also part of another study that models tree mortality and regeneration over time, predicting successional changes at the landscape level (see Information Paper 4). In conjunction with NASA, forest movement due to global warming will also be modeled.

Treeline is a place where the effects of climate change will be carefully monitored. Cold temperatures and short summers limit the chemical and biological processes that control nutrient cycling; the character of subalpine soils may directly affect the ability of plants to move upslope in the event of significant environmental warming. Relationships between subalpine fir and lodgepole pine and the microorganisms of the soils they grow in at different altitudes are being studied to help understand plants' ability to migrate in the subalpine setting. Concurrent with this research in Glacier National Park is a similar study being conducted in Olympic National Park. Together this research should offer a broader overview of projected growth patterns in the mountain regions.

These are only some of the many projects connected with study of global climate change. Glacier and other national parks will be of particular scientific value as they provide a benchmark against which to evaluate the ecological consequences of climate change in areas that have already been extensively disturbed by humans.

Conclusion

Predictions about the extent and the effects of human-caused global warming may sound improbable and apocalyptic, but many scientists feel that, far from exaggerating possible impacts, they may in fact be understating the magnitude of changes we are about to experience. Our release of CO2 and other greenhouse gases into the atmosphere has been called a grand and gigantic experiment, but it is a highly dangerous one as well. We only have one earth to play with, and we may be risking serious ecological, economic, political, and social consequences if the experiment goes awry as it seems likely to do if we fail to make rapid changes in our pattems of energy and resource consumption.

Whether or not we believe in the scientists' predictions, the two most important steps we can take to minimize the impacts of global warming are steps that we already have many good reasons for taking. One step is to minimize the habitat destruction which is already causing thousands of extinctions every year and which will exacerbate the ecological effects of climate change. The other step is to reduce our emissions of greenhouse gases immediately in order to avoid committing ourselves and future generations to an even warmer planet. Cutting back on our use of fossil fuels will improve air quality, lessen our dependence on oil imports, and reduce environmental impacts of oil, gas, and coal extraction; eliminating the use of chlorofluorocarbons will reduce our destruction of the stratospheric ozone layer; and halting tropical deforestation will save millions of species from extinction (Langley 1989; see NH 4.27.55).

Without a doubt, Glacier and other national parks are going to become increasingly valuable places for studying the impacts of global warming and other human activities, for protecting remnants of the earth's declining biota, and perhaps most importantly for motivating people to take actions like those described above on behalf of our planet and ourselves.

Author: Karen J. Schmidt.

References

Abrahamson, D.E. 1989. Global warming: the issue, impacts, responses. Pages 3-34 in D.E. Abrahamson, ed., The challenge of global warming, Island Press, Washington, DC.

Peters, R.L. and J.D. Darling. 1985. The greenhouse effect and nature reserves. Bioscience 35(11):707717.