NASA reports that the current global warming trend is proceeding at a rate unprecedented for the last 1,300 years. This rapid increase in global temperature, coupled with the complex nature by which individual species interact in their environment, makes it difficult to predict the exact response of individual species of plants and animals to climate change. We do know that habitats are shifting and ecosystems are changing as the impacts of climate change advance. And we know that strategic land conservation is a critical tool for creating a more climate resilient region, for people and wildlife into the future.
The Northwest Arkansas Land Trust has prioritized our conservation work on connected landscapes throughout the region to best meet the needs of species that might be moving with changes in temperature and precipitation. Our goal is to help ensure biodiversity and healthy ecosystems persist in our region in the face of changing climate conditions. This goal is accomplished by strategically conserving connected landscapes that capture the different geologies, elevations, landforms and “microhabitats” of our region.
What drives the presence of biodiversity?
Research by Anderson and Ferree (2010) and has demonstrated that diversity in the physical characteristics of a landscape, specifically geology, elevation and diversity in landforms, such as hills, ridges, wetlands and valleys, reliably predict higher species diversity. Examples of “geodiversity” in our region include the high elevation shale and sandstone hilltops of the Boston Mountains and the low elevation limestone caves scattered throughout the region.
How can NWALT’s strategic land conservation help safeguard biodiversity in the face of climate change?
Understanding the characteristics of climate-resilient landscapes in Northwest Arkansas will help Northwest Arkansas Land Trust and community partners prioritize places to protect in our region.
In Conserving Nature in a Changing Climate, a guide developed by the Open Space Institute and its partners, three characteristics are identified as significant drivers of climate resilient landscapes:
- Diverse physical characteristics of the land, including geodiversity (range of geology types and elevation) and landform diversity.
- Local and regional landscape connectedness.
- Biological condition of the landscape.
Our region is part of the Ozark Highland and Boston Mountain ecoregions. National Wildlife Federation defines ecoregions as geographic areas with similar climate, geology, and soils. Much of the Ozark Highlands and part of the Boston Mountains are on non-acidic limestone rock. Sections of the Boston Mountains are also over sandstone and shale. Through weathering and erosion, the underlying bedrock forms the soil, and those soil characteristics help determine which plant species can establish in a given area. Plants adapt to thrive within a specific range of soil conditions, including the moisture level, temperature, and level of acidity in the soil. By conserving landscapes representative of all geology types in Northwest Arkansas, we can better ensure a diversity of plants and animals can survive in our region in the future.
Our region was under a shallow sea over 325 million years ago. Limestone deposits were formed by the compression of the shells and skeletal remains of sea creatures.
A study by Mark Anderson and Charles Ferree of The Nature Conservancy found one of the best predictors for biodiversity is the presence of limestone bedrock, which produces soils low in acidity and high in calcium. This is reflected in our Ozark biodiversity.
The United States Geological Society indicates that over 200 species are found primarily in the Ozarks, of which approximately 160 species occur nowhere else in the world. More than 100 fish species live in Ozarks streams, including 56 species and subspecies that are rarely found outside of the Ozarks. Many bats, fish and insects, including endangered species, such as the Ozark big-eared bat, Ozark cavefish, and the Benton Cave crayfish, reside in our karst system of sinkholes, springs, caves, and disappearing streams that are created as groundwater dissolves limestone and creating underground pathways.
Because of our unique geologic history in Northwest Arkansas, our varied landscapes feature many of the characteristics necessary for climate resiliency. But we must protect them. Our region sits on the uplifted Ozark Dome. The Ozark Dome was elevated by the collision of North America with South America that produced the Ouachita Mountains about 300 million years ago. Millions of years of erosion have created the landscape we know today, with many hills, rolling plains, and low mountains. These different landscapes provide a variety of elevation ranges which helps buffer the effects of a warming climate. Elevation in Northwest Arkansas spans from approximately 1000-2300 feet above sea level. Researchers are already observing species movement to cooler elevations and latitudes in response to rising temperatures. For example, Audubon’s Birds and Climate Technical Report documents the center of the range for the Carolina Wren has moved north about 57 miles north, and the center of the range for the Pileated Woodpecker has moved north about 125 miles over the past 40 years.
Extensive erosion throughout millions of years has created hills with steep slopes facing all directions throughout our region. The different aspect, or slope direction, affects temperature and moisture levels, creating unique “microclimates” throughout Northwest Arkansas.
A microclimate is an area that has a different climate than the surrounding geographic area around it. Microclimates can be created by numerous factors, including shade from a rock overhang, proximity to a body of water such as springs and sink holes, and slope direction. For example, in the northern hemisphere, where we live, our south-facing slopes are typically warmer and drier than our north-facing slopes because they receive more heat from the sun.
Microclimates create opportunities for different plant and animal species to move to favorable nearby habitats, such as the cooler north side of a hill or mountain, or to a valley floor, or to moist, shaded sink holes. Dry rock outcroppings and rounded bluffs throughout our region, on the other hand, have a warmer temperature and less vegetation providing glade and cliff habitat for species adapted to drier, warmer conditions.
Preserving these varied landform features, and keeping them naturally connected, is critical for the survival of our native species in Northwest Arkansas. These landscapes provide habitat options for local wildlife, and provide for more southern species that might need to move into our region as their available habitats change.
The Case for Connectedness
Landscape connectivity describes the connectedness of natural habitats which enable species to move throughout a landscape without barriers. These barriers include both man-made impediments such as highways, roads, fences and development, and natural barriers, such as lakes and in some cases mountains. Migrating species need connectivity to travel to and from different geographic areas, while year-round residents also need connectivity for daily activities such as finding adequate food and water, resting, and breeding sites.
As the climate changes, connectivity becomes increasingly important for both local species relocating to nearby microclimates, as well as regional movement for species shifting their habitat to new regions.
Below are two examples of landscape-scale connectivity areas prioritized for conservation by the Northwest Arkansas Land Trust.
Biological Condition of Land
The biological condition of a landscape is a measure of the health of the ecosystem. When an ecosystem is in a healthy condition, it is more resilient to changes in climate. If the understory of an Oak-Woodland habitat, for example, is overtaken by invasive species that are not native to our region, such as Japanese honeysuckle or Chinese privet, native species cannot thrive.
The biological condition of land in our region also has a direct impact on the condition of our waterways. For example, when invasive species move into land bordering our streams and rivers, the overgrowth can shade the habitat, reducing light reaching the stream. The amount of sunlight is one variable that determines the species of aquatic plants able to establish in the stream, which in turn influences the fish species that are present.
Even when a site is in a degraded biological state, restoration can help improve the resiliency of the site. For example, Northwest Arkansas Land Trust has worked to reduce the invasive species and woody undergrowth at our Wilson Springs Preserve. This 121-acre wetland-prairie habitat is home to the Arkansas darter, a species of greatest conservation need, and many other plants and animals. Through ongoing restoration efforts, habitat for the Arkansas darter and other species has greatly improved, and native plants are reestablishing in the habitat.
Wetlands provide an important ecosystem service by functioning to slow runoff and filter pollutants before water enters local rivers and lakes. Wetland buffers are especially valuable for protecting our waterways during extreme flooding events that may affect our region with climate change.