The damage function for biosphere preservation

Below are the key takeaways and introduction to our research into biosphere preservation. Read the full report.

Our key takeaways

• The relationship between global temperature rise and species extinction rates is best described by a quadratic biosphere damage function, indicating that the rate of biodiversity loss accelerates as temperatures increase (Urban 2015).
  • Climate change is expected to have widespread impacts on biodiversity across regions and species groups, with South America, Oceania, and amphibians facing the highest extinction risks due to high endemism, limited suitable future habitat, and other factors.
  • The shape of the biosphere damage function depends on the assumptions underlying the various climate change–extinction models such as extinction thresholds, inclusion of non-endemic species, and species dispersal abilities. More conservative assumptions lead to a steeper damage function, indicating that our best estimate of the damage function might change in the future as further research refines models.
• Among the major drivers of biodiversity loss in the 21st century, climate change is likely the primary cause, followed by land use, nitrogen deposition, biotic exchanges, and atmospheric CO2. However, there is still substantial uncertainty regarding the relative importance of these factors. Our best estimate is that the importance of climate change likely lies between 0.65 and 3 times that of land use.
• The human-centric damage function is steeper than the biodiversity damage function, suggesting that human-centric damages increase more rapidly with rising temperatures compared to biodiversity damages. This difference may be explained in part by humans being more adaptable to small temperature increases, while biodiversity damages start to occur at relatively lower levels of warming.
  • The distribution of expected damages across climate change scenarios is broadly similar for both biodiversity and human-centric losses, with most damage occurring in the most likely climate scenarios. However, a slightly higher share of biodiversity damages occurs at low temperature rise scenarios compared to economic losses.
  • Because of this higher steepness, philanthropists focusing on biodiversity conservation should target their efforts slightly more towards preventing low-warming scenarios compared to those with a purely human-centric focus.

An introduction

Climate change is a major risk to the biosphere. Over the course of the 21st century, rising temperatures will likely cause significant species loss. This report aims to quantify the exact relationship between different levels of warming and the extent of biosphere degradation.

Section 1 reviews the current scientific evidence on the link between global temperature rise and species extinction rates. It focuses on a recent meta-analysis (Urban 2015) that estimates extinction risk at different warming levels—a biosphere damage function. The report then evaluates the major related studies to argue that Urban (2015) represents the best current estimate of the damage function even though there are significant uncertainties about key modelling assumptions, including species dispersal abilities, and extinction thresholds.

Section 2 assesses the relative importance of climate change versus other major threats to biodiversity such as habitat loss from increased land use. Climate change is likely the biggest driver of species extinction this century, although land use is also of large importance.

Section 3 compares the biosphere damage function to the usual human-centric damage function from climate change. The comparison reveals that a slightly larger share of the expected damages to biodiversity occurs at lower temperature increases than is the case for economic/human-centric losses. All else equal, climate philanthropists who want to focus on conservation should concentrate slightly more on interventions that affect low global warming scenarios than would be implied by a purely human-centric loss-prioritization. However, a regular climate prioritization is already very close to optimal when it comes to biodiversity conservation.

Read the full report.