An innovative paper led by Louise Mair from the School of Natural and Environmental Sciences, Newcastle University, and published today in Nature Ecology & Evolution, introduces a brand-new biodiversity metric designed to guide and steer global species recovery. The new metric, STAR (Species Threat Abatement and Restoration), quantifies the contributions that lowering species threats and restoring habitats in specific places could offer towards reducing global extinction risks. Here Professor Richard Gregory from the RSPB’s Centre for Conservation Science, and a co-author of the paper, describes this important new work.

2021 is a significant year for biodiversity because in October parties to the Convention on Biological Diversity (CBD) will come together in China to agree what many hope will be a bold and ambitious post-2020 Global Biodiversity Framework, that puts nature recovery at its heart.

The new framework, currently at a second draft stage, will likely include revised goals and targets to recover and restore healthy ecosystems, to reduce threats to species, and to recover and restore species’ populations, alongside broader goals.

Black-browed albatross in Brazil © RSPB (

Yet such noble targets have come and gone, and while significant progress has been made in saving threatened species, the tide is often against biodiversity conservation. Part of that failure is arguably because of a lack of smart tools to help guide the recovery of species and their habitats, and that is where the new metric, STAR, comes in.

In the face of a deepening biodiversity crisis it is easy to freeze and feel overwhelmed by the task of protecting imperilled species globally, but STAR pinpoints exactly how and where to act urgently, in a scientifically robust fashion. To be clear, this would necessitate concerted conservation action by many different players in society, including businesses, governments, civil society, indigenous and local communities.

In simple terms, STAR allows us to measure where and how conservation and habitat restoration could have the biggest bang for buck in reducing global species’ extinction rates.

Introducing STAR

STAR quantifies the contributions that abating threats to species and restoring habitats in specific places offer towards reducing species’ extinction risk. Higher values reflect higher contributions. To illustrate, the paper applies the metric to all species of amphibians, birds, and mammals, groups of terrestrial vertebrate species that are comprehensively assessed on the IUCN Red List of Threatened Species.

Thus, STAR is derived from existing data in the IUCN Red List and is intended to help address an urgent need. For each species, a global STAR value is defined, which varies from 0 for species of Least Concern up to 400 for Critically Endangered species using established weightings.

To calculate STAR scores for a location, the paper uses data on the extent of species’ current and restorable area of habitat, the extinction risk (IUCN Red List category) and the relative contribution of each threat to the species’ extinction risk. STAR simply assumes that for the great majority of species, complete alleviation of known threats would reduce extinction risk through halting the decline and/or permitting sufficient recovery in population and distribution, such that the species could be down-listed to the IUCN category of Least Concern.

The STAR metric is calculated for all Near Threatened and threatened species present at a location. This is known as START to denote ‘Threat’. We can also calculate STARR to denote ‘Restoration’, that is, the potential contribution of habitat restoration (and threat abatement therein) to lowering species’ threats at a location. See below:

Figure legend: Global distribution of a) START and b) STARR scores. Each species has a global START score, weighted relative to their extinction risk. This global START score can be disaggregated spatially, based on the area of habitat currently available for each species in a particular location. Total START score per grid cell (a) is the sum of the individual species’ START scores per grid cell across all Near Threatened and threatened species of amphibians, birds and mammals included in this study. Total STARR score per grid cell (b) is the sum of the individual species’ STARR scores per grid cell across all species included in this study. The global STARR score per species reflects the potential contribution that habitat restoration activities could make to reducing species’ extinction risk and is spatially disaggregated based on the availability of restorable habitat.

What does STAR tell us?

Overall, and as the maps demonstrate, STAR values are very unevenly distributed across the globe, as you might expect from known patterns of biodiversity richness and human pressures. While every nation should contribute towards halting biodiversity loss, Indonesia, Colombia, Mexico, Madagascar and Brazil combined have stewardship over 31% of total STAR values for terrestrial amphibians, birds and mammals.

Indonesian forests such as Harapan Rainforest are an important part of   STAR © Steve Rowland (

Note that countries with high STAR scores often face intense pressures on biodiversity that originate from beyond their borders, due to the global nature of demand-supply chains and global-scale threats, such as climate change. In that situation, responsibility for actions needs to be equitably shared.

This does not mean that lower-scoring countries have no species conservation responsibilities of their own as the global decline in even common species shows that all countries must act to reverse the degradation of nature and restore the diversity and abundance of species, as well as prevent species extinctions at a national scale. What’s more, nature’s contributions to people need to be valued, maintained or enhanced in their own right through conservation and sustainable use.

Turning to threats, we can use STAR to examine the main drivers of biodiversity loss and thus identify where action is most needed. For example, removing threats to threatened wildlife from crop production could reduce global extinction risk across the groups studied by 24%. Ending threats caused by unsustainable logging globally would reduce this by a further 16%, while removing threats associated with invasive alien species would bring a further 10% reduction, according to the analysis.

RSPB Forsinard Flows Nature Reserve © Kevin Arrowsmith (

In addition, habitat restoration has an important part to play in species recovery. Global extinction risk could potentially be reduced by 56% through comprehensive restoration of threatened species’ habitats, according to the paper. Actions that benefit more species, and especially the most threatened species, yield higher STAR scores. The results also suggest that safeguarding “key biodiversity areas”, covering just 9% of land surface, could reduce global extinction risk by almost half (47%)

Applying STAR

The application of STAR could have important implications for biodiversity conservation and sustainable development. In terms of the post-2020 Global Biodiversity Framework, it could help to facilitate and guide the establishment of targets to mitigate threats to vulnerable species and to halt and reverse biodiversity loss.

Importantly, STAR provides a common metric for national governments, collectively and individually, to help guide and inform their conservation strategies, especially in relation to threatened species. STAR identifies what needs to be done in principle for species and habitats to improve their status but that involves a series of assumptions that have yet to be tested and proven. In addition, the feasibility of tackling perceived threats will depend on the specific threats and the local context, including practical issues, costs, constraints and opportunities.

STAR alone does not define conservation priorities per se but goes a long way in that direction to support informed conservation planning and prioritization. In time, it is hoped that STAR might cover a wider group of taxa too and be more representative of biodiversity, beyond the vertebrates.

Significantly, the STAR approach provides a framework for the conservation of threatened species that encourages voluntary contributions from actors beyond national governments and conservation groups, such as cities, states and provinces, private businesses, indigenous and local communities. With growing and urgent calls for a pluralistic perspective to tackle biodiversity loss effectively, STAR represents a versatile new tool to meet that challenge.

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