Study definitively shows that conservation actions are effective at reversing biodiversity loss

More than 44,000 species are documented as being at risk of extinction, with tremendous consequences for the ecosystems that stabilize the climate and that provide billions of people around the world with clean water, livelihoods, homes, and cultural preservation, among other ecosystem services. Governments recently adopted new global targets to halt and reverse biodiversity loss, making it even more critical to understand whether conservation interventions are working. 

In this new study, the research team conducted the first-ever meta-analysis of 186 studies, including 665 trials, that looked at the impact of a wide range of conservation interventions globally, and over time, compared to what would have happened without those interventions. The studies covered over a century of conservation action and evaluated actions targeting different levels of biodiversity, including species, ecosystems, and genetic diversity. 

The meta-analysis found that conservation actions—including the establishment and management of protected areas, the eradication and control of invasive species, the sustainable management of ecosystems, habitat loss reduction, and restoration—improved the state of biodiversity or slowed its decline in most cases (66%) compared with no action taken at all. And when conservation interventions work, they were generally found to be highly effective. 

For example:  

• Management of invasive and problematic native predators on two of Florida’s barrier islands, Cayo Costa and North Captiva, resulted in an immediate and substantial improvement in nesting success by loggerhead turtles and least terns. 
• In the Congo Basin, deforestation was 74% lower in logging concessions under a Forest Management Plan (FMP) compared with concessions without an FMP. 
• Protected areas and Indigenous lands were shown to significantly reduce both deforestation rate and fire density in the Brazilian Amazon.  
• Captive breeding and release boosted the natural population of Chinook salmon in the Salmon River basin of central Idaho with minimal negative impacts on the wild population.  

Study co-author Associate Professor Joseph Bull, from the University of Oxford’s Department of Biology, provided crucial expertise on counterfactual impact evaluation: ‘It would be too easy to lose any sense of optimism in the face of ongoing biodiversity declines. However, our results clearly show that there is room for hope. Conservation interventions seemed to be an improvement on inaction most of the time; and when they were not, the losses were comparatively limited.’ 

Even in the minority of cases where conservation actions were not successful, conservationists benefited from the knowledge gained and were able to refine their methods. Conservationists could now implement a different strategy to remove the algae that is more likely to be successful. 

This might also explain why the authors found a correlation between more recent conservation interventions and positive outcomes for biodiversity—conservation is likely getting more effective over time. Other potential reasons for this correlation include an increase in funding and more targeted interventions. 

In some other cases where the conservation action did not succeed in benefiting the target biodiversity compared with no action at all, other native species benefitted unintentionally instead. 

According to the research team, there must be more investment specifically in the effective management of protected areas, which remain the cornerstone for many conservation actions and which this study found to work very well overall. The authors also call for further studies to assess the impact of a wider range of conservation interventions, such as those that look at the effectiveness of pollution control, climate change adaptation, and the sustainable use of species, and in more countries. 

Dr Grethel Aguilar, Director General of the International Union for Conservation of Nature (IUCN), said: ‘It shows that nature conservation truly works, from the species to the ecosystem levels across all continents.’ 

Find out more here.