Regeneration & Resilience

Newsflash:
Not All Nature-Based Solutions Are Created Equal

In a new analysis of three common nature-based climate change-mitigation strategies, only one offers the holistic benefits needed to address both the climate and biodiversity crises.

Published 1 month ago | About a 4 minute read

Image: Albrecht Fietz

In the global effort to combat climate change, large-scale, nature-based strategies such as planting forests and cultivating biofuels are an increasingly important part of countries’ plans to reduce their overall carbon emissions. But a landmark new study in the journal Science finds that well-intended strategies to increase carbon-absorbing natural capital could have unforeseen impacts on biodiversity and that, overall, restoring forests has the most beneficial effect on wildlife.

The team of authors — from The Nature Conservancy, the New York Botanical Garden (NYBG)’s Center for Conservation and Restoration Ecology, and Princeton University’s Department of Ecology and Evolutionary Biology and High Meadows Environmental Institute — argue that policymakers and conservation officials should consider impacts on biodiversity when evaluating the most effective tools to mitigate climate change: “As efforts to address climate change accelerate, it is urgent to ensure that in deploying LBMS (land-based mitigation strategies, which use plants to store carbon) we do not inadvertently imperil biodiversity.”

As understanding of the inextricability of biodiversity health and a livable climate has grown, holistic climate-action plans increasingly call for implementing nature-based mitigation strategies across millions of acres of land. The most common approaches are reforestation (restoring forests in places where they have historically grown), afforestation (adding forests in places such as savannahs and grasslands), and bioenergy cropping (farming plants such as switchgrass for renewable energy). Until now, it has been challenging to predict these strategies’ impacts on biodiversity because they affect species in multiple, complex ways.

The new study is the first of its kind to evaluate the potential biodiversity impacts of those three climate change mitigation strategies globally. The team of scientists — led by Jeffrey Smith, PhD, an Associate Research Scholar at Princeton’s High Meadows Environmental Institute — modeled the impact of these mitigation strategies on over 14,000 animal species, from creatures smaller than a mouse to larger than a moose.

Countries worldwide, from Austria to Zimbabwe, have committed to using these methods to reach their climate targets. However, as Evelyn Beaury, PhD — Assistant Curator at NYBG and postdoctoral research fellow at Princeton’s High Meadows Environmental Institute and the Department of Ecology and Evolutionary Biology — points out: “Plant-based mitigation strategies do not have the same effect on the climate or on biodiversity everywhere they are deployed. Our research suggests that we cannot assume plant-based solutions always indirectly reduce the biodiversity crisis.”

Because most modeled species inhabit forests, fostering additional forest growth in previously forested areas had a mean positive effect — whereas bioenergy cropping had a mean negative effect. Reforestation can benefit many vertebrates; but the research suggests that for most non-forest areas, doing nothing is better for biodiversity than afforestation or bioenergy cropping.

The researchers — which also include Jonathan Levine, PhD, Professor of Ecology and Evolutionary Biology at Princeton, and Susan C. Cook-Patton, PhD, Senior Forest Restoration Scientist at The Nature Conservancy — found that reforestation will benefit many species both locally, by increasing habitat; and globally, by mitigating climate change.

But the outcomes for planting monocultures of bioenergy crops or converting natural savannahs and grasslands to forests — both of which represent prescriptive efforts to increase plant life without consideration of existing biomes, and the ecosystems within — are not as rosy. While these efforts may help address climate change and reduce climate-related threats to biodiversity, they also destroy crucial habitats; replacing biodiverse meadows with bioenergy crops would be hugely detrimental for species from grouse to elk, and converting savannahs to forests would lead to the decline of iconic species such as ostriches and lions. The study found that the loss of habitat due to afforestation and bioenergy would be far greater than the benefit they would provide to biodiversity by helping mitigate climate change globally.

While ecologists have long suspected that some of these interventions would mean less habitat for wildlife, this study provides the first quantitative assessment of the potential impacts.

“Reforestation is an obvious ‘win-win’ for biodiversity,” said Beaury, an ecologist and biogeographer whose expertise includes invasive plants. “Restoring lost forest provides habitat as well as reduces the impacts of climate change.”

It has often been assumed that by addressing climate change, LBMSs will also help to stem the tide of biodiversity loss. But the report cautions that assuming a net-positive effect on global biodiversity by curbing climate change overlooks the far greater, local impact of LBMSs through habitat conversion. It is therefore critical that LBMS projects incorporate local knowledge to accurately forecast potential biodiversity outcomes and ensure that in addressing climate change we do not inadvertently worsen the biodiversity crisis.