Plant and animal species adapt slowly over time to live within a particular range of environmental conditions including temperature, water, soil type, and light levels. When the conditions of their local environment change, therefore, many species must shift to a new location to survive. According to research (Chen et al.), species are already moving to escape rising temperatures in search of more favorable habitat conditions. Species have shifted in elevation at a rate of 11 meters (about 36 feet), and toward the north and south poles at a rate of 17 kilometers (about 10 miles), per decade. Animal populations shift more rapidly than plants, because plants must spread their seeds to relocate. However, animals depend on certain plant communities for food and shelter, so this misalignment of habitat needs disturbs the balance of the ecosystem on which these species rely. Furthermore, some animals can cover ground more quickly than others. Birds, butterflies, and mammals are more mobile than small terrestrial creatures such as snails and frogs.
Northwest Arkansas is known for its abundant recreational opportunities, scenic views and biodiverse forests that provide invaluable ecosystem services for our region, including water filtration, air filtration, and carbon sequestration.
Ecosystems in Northwest Arkansas are currently experiencing multiple forms of stress, however, from urbanization, invasive species (including non-native plants and insects), diseases, and habitat loss and fragmentation. These stressors threaten the health of our Ozark ecosystems, and climate change exacerbates the region’s vulnerability.
For example, higher temperatures mean longer insect and pest seasons. Woody vines and shrubs can grow faster than trees, overtaking habitats with their fast-growing expansion. One study by Lewis Ziska measured how poison ivy grew in environments with higher levels of carbon dioxide and concluded higher carbon dioxide levels significantly increased leaf size and the amount of urushiol produced, the chemical that causes an itchy rash. Changes in temperature also enable pests from the south the extend their range northward.
Urban development and habitat fragmentation create barriers to movement for plant and animal species, which weakens their ability to migrate and adapt as their habitat ranges shift with changes in temperature and precipitation. Current urbanization has decreased water quality by reducing the natural buffers responsible for filtering out pollutants. In the future, these negative impacts on water quality will be compounded during extreme flooding events associated with climate change.
Impacts to Our Ozark Forests
As the observed changes in plant hardiness zones indicate, plant species historically found in South Arkansas are advancing northward. The degree of change we will experience in Northwest Arkansas varies based on carbon emission/reduction scenarios and how well we do on that front.
Scientists have analyzed tree ring samples from specific tree species in the Ozark Highlands to estimate how trees have responded to past temperature fluctuations and drought conditions by comparing tree growth to historical climate data. This research provides insight into which tree species are more likely to thrive over time in a warming Ozark climate.
Preliminary data suggests drought-adapted post oaks could expand in range, where black walnuts would be less adaptable because they require more moisture. The recent drought in 2012 killed large populations of white and red oak in the Ozarks, indicating they may also be more vulnerable to the predicted increased periods of intense drought in Northwest Arkansas. The loss of walnut, white oak, red oak and other native Ozark hardwood tree species would have an economic and ecological impact on our region.
In addition, the increased proliferation of invasive plant species, as mentioned above, already threatens to overtake our Ozark understory trees, such as Redbuds and Dogwoods, and shades the wildflowers and other plants characteristic of our Ozark woodlands in early spring.
Impacts to Our Aquatic Ecosystems and Water Quality
Increased temperatures and varying precipitation levels have a direct impact the health of vulnerable aquatic habitats in Northwest Arkansas.
When water temperatures increase with increasing air temperature, the amount of available dissolved oxygen in the water decreases. Aquatic fish, insects, bacteria, and plants require a specific range of dissolved oxygen to survive. Warmer temperatures can also lead to an overgrowth of algae, which negatively impacts water quality, including consumption of available dissolved oxygen.
Extreme rainfall events increase the runoff of pollution into our waterways, including sediment, nitrogen-rich fertilizers and agricultural waste, further degrading water quality. These pollutants already impact our waterways negatively, and problems will predictably intensify with increased flood events.
According to the Arkansas Wildlife Action Plan, fish species that rely on shallow pools and streams would be most impacted by altered flows and drier conditions associated with climate change. Like terrestrial animals, fish can move in search of new habitats with more favorable conditions, but man-made barriers such as dams and changes in hydrology often prohibit their ability to relocate. Rising water temperatures could also impact local sport fishing and tourism revenue. As an example to consider, a U.S. Forest Service study found that between 53 and 97 percent of natural trout populations in the Southern Appalachian region of the U.S. could disappear with warmer temperatures predicted by global climate change models.
Impacts on Livestock Farming
Agriculture is an important economic driver in Northwest Arkansas and an important part of our cultural heritage. According to the Washington and Benton County profile reports, farm income from 2010 livestock and product sales was estimated at $834 million in Benton and Washington counties. Temperature and precipitation predictions could have a direct economic impact on farmers in Northwest Arkansas.
Research by the University of Arkansas Extension office reports that in the state of Arkansas, the 2012 drought resulted in an estimated $128 million loss in the cow-calf sector. The average loss for the for cow-calf producer was $141 per bred cow.
Warmer temperatures also impact milk productivity. As temperatures rise from 90° to 100°F and humidity remains in the 50 to 90 percent range, dairy cattle consume less and in turn milk production usually decreases by greater than 25 percent.
Impacts on Crop Farming
Some studies suggest that increases in atmospheric carbon dioxide levels could increase production of certain crops, but higher temperatures and increased drought also amplify crop heat stress, irrigation requirements, and susceptibility to pests. Many weeds and pests also flourish in warmer climates, and new ones introduced, posing additional ongoing difficulties for farmers. The nutritional value of crops may also be impacted. According to the EPA’s Climate Change Impacts Agriculture report, higher CO2 levels have been associated with a reduction in protein and nitrogen content of alfalfa and soybean plants, degrading the quality of these crops.