Bad news about biodiversity seems to hit every week—plants and birds and insects and fish are all imperiled due to habitat loss or lack of water or overharvesting. To slow the planet’s loss of species richness, governments around the world have added more than 18 million square kilometers of protected land since 1990, according to a U.N. report. But research that will be published in January in the journal Nature shows that it’s not enough to set aside sanctuaries and hope for the best. The strongest factor in stemming biodiversity loss, the findings show, is a robust set of conservation laws that are consistently enforced.
Tatsuya Amano, principal author on the paper and a post-doctoral fellow at the Department of Zoology and the Centre for the Study of Existential Risk at the University of Cambridge, used data collected from wetlands across the globe and looked to answer a related pair of fundamental questions: Where are we gaining or losing the most species, and why? Amano compared the influence on biodiversity of three kinds of factors: human impacts like land-use changes; biological characteristics of species such as their size or migratory status; and conservation factors like protecting land or enacting and enforcing conservation laws.
To get at the answers, Amano mined the more than 2.4 million records of 461 species of wetland-dwelling birds at 25,769 survey sites across the planet. He chose wetland birds because those habitats are globally threatened, and because there has been a concerted effort over decades to monitor wetland bird declines. The data came from the International Waterbird Census, coordinated by Wetlands International, and Audubon’s Christmas Bird Count. Both surveys occur in December and January, which made the datasets relatively easy to integrate into a single analysis. Even so, Amano needed almost six years to complete the study because the datasets were so large.
“I was surprised that governance correlated so closely with biodiversity,” Amano says. He checked his model repeatedly, convinced there was some error in the data that miscalculated both the role governance played and where the most biodiversity loss was happening. Amano says he expected the most wetland biodiversity loss to occur in the tropics, which are a well-known hotspots for loss of biodiversity in general, or in East Asia and Oceana because of the region’s rampant economic growth and the development and agricultural pressures that come with it. Instead, he found that parts of Central/Western Asia, South America, and Africa were hardest hit. As an example, Amano pointed to the significant loss of wetland birds in Iran, a country with ample wetlands set aside for conservation purposes, but weak enforcement of anti-hunting laws. On the other hand, wetland birds did well in areas with strong environmental protection agencies, like the European Union, and portions of North America. (Amano notes that if governance weakens in North America, in the future we could see significant biodiversity loss on our own shores.)
Candan Soykan, a quantitative ecologist and co-author on the paper, said Amano’s work showed the same general trends as the Christmas Bird Count trend analysis Soykan undertook a couple of years ago when he was part of the Audubon science team. In that analysis, Soykan and colleagues analyzed Christmas Bird Count data from the mid-1960s until 2013 to understand how bird populations have changed over the last few decades. That the two researchers found similar waterbird trends bolsters both analyses, he says.
Regarding Amano’s ability to correlate biodiversity changes with a specific set of factors, Soykan says, “I’ve heard about these kinds of results anecdotally, but it’s great to see quantitative analysis at a global scale.”
For the future, Amano wants to see if he can use a similar method to track the effects of climate change on wetland birds across the globe. Both he and Soykan say that such an analysis would require teasing out what environmental factors can be tied definitively to climate change, which they both admit is difficult to do.
In the meantime, Amano says, conservation groups that want to preserve biodiversity can use the data as a springboard for action: It’s not enough to just set aside land, or manage water quality, or curb emissions. You have to make sure that local authorities enforce existing legislation, and work to make laws stronger. Only then will we be able to stem the tide of extinction.