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US researchers unveil study on impact of bioenergy demand on wildlife

Prothonotary Warbler thrives in different habitats . Image retrieved of Flickr copyright Phillip Kenny
Prothonotary Warbler thrives in different habitats . Image retrieved of Flickr copyright Phillip Kenny

Researchers from North Carolina State University and the US Geological Survey (USGS) have published a study on how wildlife is impacted by bioenergy demand.

The researchers find that choosing how to meet bioenergy goals means making trade-offs about which wildlife species and ecosystems will be most impacted.

The work focuses on the southeastern US, but yields general insights that could inform bioenergy policy globally.

“Bioenergy can refer to wood pellets burned to generate electricity or to liquid biofuels, and bioenergy sources range from crops like switchgrass and sweet sorghum to cultivated pine forests and natural pine and hardwood forests,” said Nathan Tarr, lead author of one paper on the work.

He added: “There are questions about how renewable energy targets that promote bioenergy may affect wildlife habitat and forest ecosystems. We wanted to better understand the potential impacts of bioenergy demand in North Carolina and, by extension, in the Southeast and beyond.”

Tarr is a research associate in the North Carolina Cooperative Fish and Wildlife Research Unit at NC State.

To address these questions, the researchers first developed models that allowed them to translate bioenergy demand into projections of changes in the size and characteristics of ecosystems.

The researchers found that the specific mix of biomass sources used to meet demand could play a significant role in shaping ecosystems, especially in forests that contain high biodiversity.

Harvesting biomass

“Our model results show that meeting bioenergy demand by harvesting biomass from forests retained more forest on the landscape, but the remaining forest contained less of the mature floodplain forests and longleaf pine forests that harbour biodiversity,” said Jennifer Costanza, lead author of a second paper on the work and a research assistant professor of forestry and environmental resources at NC State.

She added: “On the other hand, using agricultural crops to meet demand reduced overall forest area, but spared more of the high-biodiversity forest land.

“Each of the biomass sources we looked at caused substantial land use change, especially in the coastal plain region, which is known for its high biodiversity and was recently designated a global biodiversity hotspot.”

The researchers then used the projected forest changes to model habitat gains and losses for 16 wildlife species.

They were also able to assess what the use of different biomass sources might mean for various wildlife species.

‘Trade-offs’

The researchers found that realistic levels of bioenergy demand are large enough to cause large gains or losses of habitat for some species, and the specific mix of biomass sources used to meet demand resulted in trade-offs regarding wildlife habitats.

“None of the biomass sources that we looked at were good or bad for all species, nor was a single mix of biomass sources consistently the best or worst for all species,” Tarr said.

She added: “For example, sourcing biomass by increasing the amount of forests harvested in the state resulted in projected losses of habitat for the prothonotary warbler (Protonotaria citrea), which prefers mature, floodplain forests. But harvesting forests increased habitat for the yellow-breasted chat (Icteria virens), which thrives in regenerating forests, and had little effect on the amount of habitat for the mole salamander (Ambystoma talpoideum), which inhabits upland forests.”

“While the models used data from North Carolina, this work highlights four general principles that need to be considered when evaluating the wildlife implications of bioenergy demand.”

The researchers found the following:

  • Species that inhabit newly regenerating forests may benefit from bioenergy demand;
  • Species that rely on a single, mature type of habitat – such as bottomland hardwood forests – are at risk if that type of habitat is harvested for bioenergy;
  • Bioenergy demand could exacerbate habitat loss for species that are losing habitat to urbanization; and
  • Species with small ranges deserve special consideration because they can be more sensitive to landscape changes related to bioenergy harvesting.

‘Wildlife conservation’

“This highlights the importance of setting priorities for wildlife conservation,” said Matt Rubino, co-author of the paper and a research associate in the North Carolina Cooperative Fish and Wildlife Research Unit at NC State.

He added: “Because any mix of biomass sources is likely to benefit some species and harm others, it is important to identify which species are priorities for conservation so that policies can be designed to minimize negative impacts on those species.”

The papers, Projected Gains and Losses of Wildlife Habitat from Bioenergy Induced Landscape Change and Bioenergy Production and Forest Landscape Change in the Southeastern United States are published in the journal Global Change Biology Bioenergy.

Both papers were co-authored by Robert Abt of NC State; Jaime Collazo of the USGS and the North Carolina Cooperative Fish and Wildlife Research Unit; and Alexa McKerrow of USGS. The work was done with support from the USGS Gap Analysis Program.

Prothonotary Warbler thrives in different habitats . Image retrieved of Flickr copyright Phillip Kenny