Eastern Forests and Climate

The Chimney Rock overlook at sunrise, with a light dusting of snow.
Chimney Rock is the result of hundreds of millions of years of tectonic forces and erosion. Freeze-thaw cycles in the winter continue to shape the formation.

NPS/Connor Henzel

Born of a Dynamic Climate

Long-term changes in the terrain and climate are normal and have been occurring since the beginning of the Earth itself. However, human influences on the environment are occurring at a faster rate than any other time in history: faster than life can adapt to them. The natural rate of evolution simply can’t keep up with some of the changes now occurring. Under current climate models, water temperatures in Big Hunting Creek at Catoctin are projected to become too warm for native brook trout (docx. 5.52MB) to survive there.

Catoctin Mountain Park was born from changes in the position of the tectonic plates that make up the Earth’s crust. The rocks of Chimney Rock were once beach sand that settled to the bottom of the sea. It became deeply buried, and was compacted over time into sandstone. The later collision of North America and Africa squeezed the rocks into a great mountain belt, the ancestral Appalachians. This squeezing also changed the minerals of the rocks themselves: sandstone turned into quartzite. Weather, erosion, and time later wore the mountains down to their present height.

Weather continues to play an important role in the evolution of Chimney Rock. Water seeps into tiny cracks along regular planes in the formation. When this water freezes in the winter, it expands and forces the cracks apart. This frost wedging creates the angular patterns in the rock we see today.


Monitoring Change

Understanding the condition of natural resources in national parks is fundamental to the National Park Service's ability to fulfill its mission to conserve park resources and leave them "unimpaired for the enjoyment of future generations." In support of parks, the National Capital Region Inventory and Monitoring Network monitors ecosystem "vital signs" including water, air, plants, animals, and various ecological, biological, and physical processes. These vital signs represent the overall health or condition of park resources, and allow park managers to track the condition of resources over time.

Park biologists, and researchers from federal agencies and universities conduct additional on-the-ground research in the park, including water quality tests, deer population surveys, disease research, and invasive plant mapping. These studies inform management decisions at Catoctin Mountain Park and tell the broader story of natural and cultural resources in the Appalachian region.


Future Challenges to Eastern Forests

Climate change increases the uncertainty about the future of the region’s forests. Longer growing seasons and higher atmospheric CO2 concentrations may increase productivity. However, the changing climate tends to intensify or add to stresses that already exist for a species. Less healthy tees have increased vulnerability to drought, changes in suitable habitat, invasive species, pests and pathogens, wildfire, and air pollution.

The loss of trees in Catoctin Mountain Park reduces habitat availability for native flora and fauna and results in a less rich forest ecosystem.



Decreasing soil moisture and increasing plant demand for water as the growing season lengthens are likely to worsen summertime drying and contribute to drought-induced plant stress. Although overall precipitation is increasing in the central Appalachians, extreme weather events and erratic timing between rainfalls is also on the rise, potentially leading to more drought events.


Timing of Biological Events

Wildlife that depend on seeds, nuts, fruit, and nectar from plants synchronize their life cycle with the availability of these resources. For example, some insects time their spring emergence with the development of certain plants. As the annual timing of seasonal weather patterns shifts, these critical synchronizations may unravel.

A black bear rummages through food left by campers on a picnic tables
Properly storing food and disposing of garbage can be life or death to a bear.

NPS Photo

Black Bears and Hibernation

As winters become warmer, and more compressed, hibernation cycles are disrupted. Bears are going into hibernation later in the winter, and waking up earlier in the spring. This increases the risk for human-bear encounters as the animals are more active throughout the year and changes in food availability force them to forage in closer proximity to human populations.

Black bears prefer to avoid people, and rarely cause human injury. You may have even happened across one on the trail without even knowing it! A black bear will get away at the first sign of an approaching hiker, well before you notice it.

Storing your food and disposing of garbage properly can mean life or death to a bear. Bears learn quickly and will return to areas where they find food. Not only can this be dangerous for people, but it is also harmful to bears that may need to be euthanized if they become too habituated to people and forage in campgrounds. Follow bear safe practices when traveling in bear country and camping in the park.

The emerald ash borer insect and the holes it makes in the bark of trees.
A close up of an Emerald Ash Borer insect and the feeding tunnels the insects create under ash bark.

Top: David Cappaert, Michigan State University.
Bottom: NPS Photo

Invasive Species, Forest Pests, and Plant Pathogens

Climate change in the mid-Atlantic is likely to lead to increased exposure and susceptibility to invasive species, pests, and pathogens as trees are put under greater stress. Invasive species may have a negative effect on plant productivity if individual trees face increased competition from nonnative plants and woody vines. Invasive plants at Catoctin include Japanese barberry, mile-a-minute, and garlic mustard.

Pests and pathogens, such as the hemlock woolly adelgid or pine blister rust, are already having major effects on forest productivity in the United States and Canada. Climate change is likely to increase their impact as rising temperatures reduce winter pest die-off.

The emerald ash borer is one of many exotic threats to Catoctin Forests. These small green insects arrived hidden in wood packing materials from Asia and are responsible for the destruction of tens of millions of ash trees in 30 states. Ash trees are some of the most valuable and abundant North American woodland trees. Ecologically, they host 150 species of native moth and butterfly larva, a food source important to birds. The emerald ash borer beetle cannot fly very far, but it can travel great distances hidden under of the bark of firewood. Never move firewood from one area to another and only buy firewood from local sources and burn it where you buy it.

A park ranger firefighter starts a prescribed burn in a dry field with a drip torch
Prescribed burning is one way to reduce fuel loads in a controlled environment and prevent wildfires that are more severe.

NPS Photo


Due to a longer growing season and increased risk of drought, the fire season has become longer and your risk of exposure is greater. Additionally, the spread of exotic species increases fuel loads through the increase of biomass and mortality of native plants, while winter storms and wind events cause more downed woody debris.


Air Pollution

Air-borne pollutants can change productivity and influence how trees respond to climate change.

  • Acid rain already occurs across the central Appalachians and may increase, if climate change produces more cloud cover and precipitation. Acidic rains can impair nutrient availability, reduce reproductive success and frost hardiness, cause physical damage to leaf surfaces, and increase tree mortality.
  • Ozone can damage plant tissue and decrease photosynthesis. Although carbon dioxide (CO2) emitted into the atmosphere through human activity may plant growth and forest productivity, studies suggest that ozone damage will offset these gains and make trees more vulnerable to other stresses. Ozone levels, which are already high, may increase with climate change as plants produce more volatile organic compounds, which then react with the air to produce ozone.
    • While ozone in the upper atmosphere is natural and beneficial, ground level ozone is harmful to human health, and is increasing due to emissions of volatile organic compounds and nitrogen oxides. Industrial facilities and electric utilities, motor vehicle exhaust, gasoline vapors, and chemical solvents are the primary sources of these emissions.

  • Catoctin Mountain Park’s scenic vistas, including Chimney Rock, Thurmont Vista, and Blue Ridge Summit Overlook are impacted by air pollution. Skies are set to become increasingly hazy due increased pollutants and temperatures, reducing visibility and negatively impacting viewsheds.
Winston Churchill and FDR fish on a rock alongside Big Hunting Creek
Winston Churchill and Franklin D. Roosevelt fishing on Big Hunting Creek. They didn't catch anything, but took this photo was taken to prove that they tried.

Public Domain Photo

Brook Trout and Stream Temperature

A recent U.S. Geological Survey report found that increasing temperature may negatively affect the population of native brook trout (docx. 5.52MB) native brook trout Big Hunting Creek, one of the most significant freshwater fisheries in Maryland.

Big Hunting Creek has played a prominent role in the development of recreational trout fishing in Maryland. The stream has long been popular among fly fishers. It is the birthplace of the Brotherhood of the Jungle Cock, an organization dedicated to helping young people understand and appreciate the sport of angling and the resources upon which it depends. Big Hunting Creek was the first stream in the State of Maryland to be designated as fly-fishing only. Later it became Maryland's first catch-and-release trout stream.

Researchers studied fish populations in the watershed and modeled how future temperature increases would affect brook trout. These fish depend on cold water environments to survive, and are already under stress from invasive brown trout encroaching on their habitat.

Fisher holding a trout just caught from the stream.
Warming streams may limit available habitat for brook trout, a species with significant cultural importance.

NPS Photo

Their findings show reduced habitat for brook trout on the mountain:

  • With just a 1.5 °C (2.7 °F) projected increase in air temperatures, most of upper Big Hunting creek will no longer be able to support brook trout. Owens Creek and Blue Blazes Creek would remain suitable habitat.
  • If air temperatures increase 3°C (5.4°F), Owens Creek and Blue Blazes Creek would become too warm in some spots.
  • At a 5°C (9°F) increase, most sites on Catoctin would become too warm for brook trout.

Researchers also anticipate increasing winter storms will harm fish populations. Extreme rain events can send a gush of water into streams that wipe out fish eggs from the streambed. These wash-out events are some of the most important factors that affect populations. You can help protect spawning grounds by not walking in streambeds.


Preserving Historic Structures

In the 1930’s, cabin camps were built in Catoctin to encourage people to go outdoors and enjoy nature. Visitors have enjoyed these cabins for decades, but climate change threatens these historic structures, creating new challenges to preserving our historic structures.

How does climate change affect Catoctin’s Historic Structures?

  • Increased temperature and humidity is affecting building materials and accelerating rot.
  • Severe weather Climate change has already resulted in a 71% increase in the frequency of heavy downpours in the Northeast corridor of the USA from 1958-2012. The frequency of intense storms is likely to continue to increase over the next several decades, resulting in erosion that damages the foundations of our cabins.
  • Pests The increase in temperature and humidity would also bring increased pests that thrive in warmer weather. Pests, such as termites, could increasingly damage the cabins’ irreplaceable American chestnut lumber.
View of Chimney Rock in the Fall on an overcast day.
Fall color is an important part of regional tourism and outdoor recreation.

NPS/John Zuke

Economic Impacts

The forest products and forest-related recreation industries are major contributors to the region’s economy, providing 18% of all jobs in western Maryland. While extended growing seasons and the potential fertilization effect of CO2 should enhance forest productivity over the next century, several major confounding factors could work against this beneficial response, including increasing pressure from pests, pollution, greater competition from invasive species, acid rain, increased drought and fire potential, and altered winter freeze-thaw cycles.

The local travel and tourism sector generates employment in retail trade, passenger transportation, arts and entertainment, recreation, food service, and lodging. Visitors to the park are an important part of this economy, bringing tourist dollars to local communities. Impacts on forest health and changes to viewsheds from pollution could negatively affect recreation activities and visitation to the park. The fall color season is one of the most significant draws for visitors to Catoctin Mountain Park. New weather patterns, including later fall cooling and increased risk of drought could lead to less brilliant fall foliage and reduced visitation.

Extreme closeup of a deer tick on a blade of grass.
Health and Climate Change

Mosquito and tick-borne diseases are on the rise in a warming climate.

An electric car is plugged in and charging.
Sustainability in the Park

From alternative fuels to energy saving appliances, the park is working towards a low carbon future.

A group of volunteers holds shovels and loppers.
How You Can Help

You can be a part of the solution. At home, on the road, and in the park – get involved!

Close up of a solar flare
Climate Change

The greenhouse effect is becoming stronger due to human activity.



U.S. National Park Service. Climate Change Trends for Resource Planning at Catoctin Mountain Park, Maryland. Climate Change Response Program. Washington D.C., 2012.

US Global Change Research Program. Climate Change in Eastern Forests and Woodlands. Washington D.C., 2008.

U.S. Forest Service. Central Appalachians Forest Ecosystem Vulnerability Assessment and Synthesis: A Report from the Central Appalachians Climate Change Response Framework Project. Northern Research Station, 2015 (General Technical Report NRS-146).

U.S. Forest Service. Central Appalachians Forest Ecosystem.

U.S. Forest Service. Changing Climate, Changing Forests: The Impacts of Climate Change on Forests of the Northeastern United States and Eastern Canada. Northern Research Station, August 2014. General Technical Report NRS-99.

Inkley, Doug, et al. Nowhere to Run: Big Game Wildlife in a Warming World. National Wildlife Federation, 2013.

Inkley, Doug, et al. Nowhere to Run.

Emerald Ash Borer.” Tree Health Guide, Arbor Day Foundation, 2015.

Office of Plant Industries and Pest Management. “Emerald Ash Borer.” aryland Dept. of Agriculture.

U.S. Forest Service. Central Appalachians Forest Ecosystem.

U.S. Forest Service. Changing Climate, Changing Forests.

Melillo, Jerry M., Terese (T.C.) Richmond, and Gary W. Yohe, Eds. (2014). Climate Change Impacts in the United States: The Third National Climate Assessment. U.S. Global Change Research Program, doi:10.7930/J0Z31WJ2.

U.S. Forest Service. Central Appalachians Forest Ecosystem.

Last updated: April 26, 2024

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