MISSOULA – Scientists have long assumed that national parks help conserve wildlife and protect biodiversity. But is that truly the case?
Fresh research from the University of Montana, international partners and NASA-affiliated scientists suggests that parks do indeed enhance bird diversity inside their borders. Large parks also support higher diversity of both birds and mammals in nearby unprotected areas.
The research was published Aug. 23 in Nature.
"We knew that protected areas can reduce logging – you can see that from satellite imagery – but you can't see the animals in the forest from space," said the study's lead author Dr. Jedediah Brodie, the UM Craighead Chair of Conservation. "Our new analysis shows that parks benefit forest wildlife, too."
Brodie also is a Universiti Malaysia Sarawak (Malaysia) research fellow. He said that some scientists have argued that conservation success inside some parks can come at the expense of neighbouring unprotected habitats – that parks displace extractive impacts like hunting, fishing and logging to other nearby areas.
But on the other hand, marine parks often report biodiversity "spillover," meaning that species protected within park boundaries produce an abundance of eggs, larvae and adults that then disperse and increase the biodiversity in surrounding habitats.
"So the question is, 'Do terrestrial land parks displace biodiversity losses or provide biodiversity spillover?'" Brodie said.
The new study recruited scientists from 10 countries to conduct a comprehensive analysis of bird and mammal diversity inside and outside of parks across Southeast Asia, one of the most biodiverse regions on Earth. The scientists compiled a massive database of bird and mammal observations across the region that demonstrated the protective features of national parks.
Brodie said the findings are especially timely for the United Nations, which recently announced ambitious biodiversity conservation targets that include significant expansions of global protected areas. The UN strategy is to conserve 30% of Earth's lands and waters by 2030, the so-called "30 by 30 goal."
"Massive expansions to global protected area coverage will be difficult and expensive, but our results show that it's worth it," Brodie said.
Indeed, the work provides clear justification to designate protected areas that are as large as possible, as larger parks had significantly stronger influence on mammal diversity in the surrounding landscape. Recent work in the region suggests that some wildlife species are persisting in small parks, but this apparently doesn't scale up to such areas having landscape-scale "spillover" effects.
The time to move forward with protected area expansion is now, said co-author Professor Mohd-Azlan Jayasilan of the Universiti Malaysia Sarawak.
"If governments responsible for gazetting protected areas think that it is difficult to protect large areas now, it's simply going to get more difficult with exasperating socio-political setbacks in the future," Jayasilan said.
"Not all parks are equal," said co-author Dr. Mairin Deith of the University of British Columbia, Canada. "Larger parks routinely had higher bird diversity. Considering the UN's goal of increasing protected area to 30% of the world's surface, these findings support the creation of fewer larger parks compared to many smaller ones, where it is possible to do so."
At the same time, she said, there might be other invisible social forces researchers couldn't see from their dataset that may be related to park size, such as differences in funding, enforcement and local buy-in to protections.
Hunting is a key concern for Southeast Asian wildlife conservation and a prime suspect for why diversity has often been assumed to decline outside of parks. Hunters are mobile, so hunting bans within park boundaries may only displace these activities to nearby unprotected areas and undermine their net benefit.
"To be honest, I was surprised that mammal diversity was higher outside large parks," said co-author Dr. Matthew Luskin of the University of Queensland, Australia. "It's common to see hunters inside and outside of parks in many countries. I expected that hunters' selectively removing game animals would reduce diversity. However, it appears parks limit hunting so it does not drive complete extirpations in most cases."
NASA's Global Ecosystem Dynamics Investigation operates a near-infrared laser instrument on the International Space Station, providing vertical information on forest structure that the study used in its analysis. Co-author Scott Goetz of Northern Arizona University noted that "while satellite monitoring of forest cover is essential for tracking deforestation, the unique data provided by GEDI allows us to go beyond cover and get at the structural diversity and habitat heterogeneity of forests, which is important for biodiversity."
Co-author James Ball of the University of Cambridge said, "Integrating NASA's GEDI data into this analysis allowed us to control for 3D forest structure in a way that simply wasn't possible a few years ago. This reassures us that the results hold across different forest types."
