How bioenergy demand could affect wildlife habitat

Sweet sorghum, switchgrass and trees are among some of the products that are used as fuel for bioenergy, or renewable energy produced by living organisms.

In a recent study published in Global Change Biology Bioenergy, researchers looked at how demand for this organic material, or biomass, might affect wildlife habitat in North Carolina. “There is currently a lot of foreign and domestic demand for bioenergy,” said lead author Nathan Tarr, who is a research associate in the North Carolina Fish and Wildlife Research unit at North Carolina State University and a TWS member. According to Tarr, North Carolina is one of several southeastern states with wood pellet facilities. These pellets are sometimes shipped to Europe to meet renewable fuel and sustainability targets, he says.

As part of their study, Tarr and his colleagues looked at how different strategies for meeting bioenergy demands would affect habitat availability for wildlife. “We know that different species have different habitat preferences,” he said. “What we were interested in doing was integrating models to explore how different their responses would be to realistic bioenergy demands.”

To do this, Tarr and his team used a timber supply model, created by scientists at North Carolina State University, which translated demand for timber into changes to the landscape. They also simulated changes to the structure and age of plant communities over time and used species-habitat models to estimate future changes in habitat availability. In addition, the team combined the models to determine how species fared with realistic bioenergy demand, according to Tarr. For example, they examined which species would be moved to marginal lands to make way for switchgrass and other bioenergy crops and whether that move would have any impact on overall survival.

Each scenario of bioenergy demand and biomass sources had winners and losers. For example, harvesting planted pine and natural hardwood forests in an effort to produce more bioenergy would potentially benefit species that use early successional or regenerating forests such as the yellow-breasted chat (Icteria virens), but would cause species that prefer mature forests such as prothonotary (Protonotaria citrea) or cerulean warblers (Setophaga cerulean) to lose considerable amounts of habitat. “The realistic levels of [bioenergy] demand had consequences that could be important for the species,” Tarr said. Further, many people expect the demand for wood pellets to increase, he says.

Tarr also says that the conversion of marginal lands to bioenergy crops would decrease habitat availability for grassland species such as the grasshopper sparrow (Ammodramus savannarum) or loggerhead shrike (Lanius ludovicianus), which are losing habitat to urbanization.

Another important take-home message from the study, Tarr says, is that species with smaller ranges and specific habitat requirements are especially susceptible to the placement of bioenergy harvests. Some of these species include the gopher frog (Rana capito), oak toad (Anaxyrus quercicus) and prothonotary warbler, “but the effects could be positive or negative, depending on the species,” he said.

According to Tarr, it’s important to recognize that different demands for bioenergy as well as how those demands are met have different implications for different species. “One important thing that came out of this is that given the variation of responses and tradeoffs involved, it’s really important for anyone making assessments of bioenergy effects on wildlife to carefully consider which species to include in the assessment,” he said. “This could shape the results of the assessment.”