Next year, all eyes will be on Kunming, China, as talks resume on a new set of global goals to protect biodiversity. These are much needed, because most of the existing 20 targets, which were set in 2010 in Aichi, Japan, have failed to make an impact on the rate of biodiversity loss.
Last month, a team of researchers proposed creating one headline number, suggesting that countries should aim to keep extinctions to “well below” 20 known species every year worldwide1. This would be the biodiversity equivalent of the 2 °C climate target: a simple, measurable goal that can be understood by the public and politicians alike.
The proposal, by Mark Rounsevell at the Karlsruhe Institute of Technology in Germany and his colleagues, is intended to break nearly two decades of failure in global biodiversity policy and target setting — the 2010 Aichitargets replaced a previous unsuccessful target to slow the rate of biodiversity loss that countries set themselves in 2002. And the idea is gaining traction.
In an interview with Nature, Elizabeth Maruma Mrema, the new head of the United Nations Convention on Biodiversity, acknowledged that it would be difficult to set a single target because biodiversity is multifaceted. But, if the community succeeds in making it work, she adds: “that will be the best result possible because then it becomes a song everyone will sing, and that everybody can align with to deliver that one key message.”
A target for limiting extinctions is not a new idea, and deserves serious consideration. Its feasibility and consequences should be rigorously assessed by the convention’s own scientific advisory body, and by the Intergovernmental Science-Policy Platform on Biodiversity and Ecosystem Services (IPBES), in the same way that climate metrics are assessed by the UN’s climate-science advisers, including the Intergovernmental Panel on Climate Change (IPCC).
There are many questions for researchers working in biodiversity to explore. For example, how does a target of 20 extinctions per year — across all plants, animals and fungi — fit with IPBES’s own assessment of biodiversity, which says that some one million species are at risk of extinction? Twenty extinctions per year — out of almost two million known species — is ten times higher than the background extinction rate of two per year that existed before humans made a notable contribution to extinctions. But it is considerably lower than today’s estimates ofspecies extinctions, which are in excess of 1,000 times the background rate.
Other questions include how to choose which species to conserve, and who should make such choices. Would a single number give equal weight to all threatenedspecies, or should those species that are more important to livelihoods and to ecosystem function be given priority for protection? As the authors point out, it is possible for biodiversity loss to result in large and damaging changes to life on Earth without any species going extinct. And at what point would an extinction be declared, given that there is often a time lag between a species going extinct and its being recorded as extinct in the Red List maintained by the International Union for Conservation of Nature?
Given that IPBES’s lower estimate for as-yet unidentified plant and animal species is 8.1 million, what are the implications for species that have not yet been described? Ifpolicymakers focus resources on conserving known species, what risks might there be to species in parts of the world — such as the marine environment — where knowledge of biodiversity is weak, and which face continued unsustainable development?
And what would the implications of a single target be for the convention’s other objectives? Conserving species is one of three aims, alongside ensuring that biodiversity is used sustainably and ensuring that benefits (such as commercial products) are shared fairly, so that no one — for example, Indigenous communities — is left out.
Biodiversity is essential to economic prosperity, food and human health, and the researchers are keen to stress that the creation of one extinction target should not detract from the need for governments to create nationally relevant targets and policies. They also advocate the provision of funding to help countries that are financially poor but biodiversity-rich to meet their goals.
Certainly, a single target, such as that for climate change, would be simpler to communicate than the Aichi targets. And the authors are right to acknowledge that, ultimately, biodiversity loss continues because public-policy decisions — for example, decisions that lead to industrial economic growth — have not accounted for the costs of replacing the services that species and ecosystems provide to humans.
But they will also know that, although the target to keep global temperatures to within 2 °C of pre-industrial levels was agreed by members of the UN climate convention, that number was subjected to a thorough process of research evaluation by a wide group of researchers in the IPCC before it was adopted.
Any proposal to consider a single numerical target for biodiversity needs to be similarly assessed. IPBES — working with the UN biodiversity convention’s own scientific advisers — should be called on to advise. For this to happen, a small group of governments need to make a formal request for scientific advice to the UN convention, and they should do so without delay.