Protecting nature outside national parks

In findings that have implications for Nepal’s protected areas, a new study has found that improving the landscape surrounding forest remnants can increase their ability to retain bird species — even in small or isolated forests.

For decades, traditional ecological theory has treated isolated and fragmented habitats as ‘ forest islands’, predicting species’ survival through area size and isolation. 

But these models have long overlooked the nature of the matrix of farmland, vegetation, or open areas surrounding these habitat remnants.

Such isolated natural habitats can be found in Nepal’s buffer zones and the fringes of community forests. The study shows that such landscapes are critical, as species must move through, use, or avoid them when navigating between forested areas.

The research published on Monday in Proceedings of the National Academy of Sciences (PNAS) provides strong evidence that the quality and structure of the matrix play a crucial role in biodiversity survival.

The study was led by scientists from the Instituto Federal de Educação, Ciência e Tecnologia Farroupilha in Brazil, Slippery Rock University in the US, and University of East Anglia (UEA) in the UK. 

It shows that even modest increases in nearby tree cover can substantially boost the number of bird species that survive in forest remnants.

“This study clearly shows how high-quality surrounding landscapes increase species retention within forest remnants,” said Prof Carlos Peres of UEA’s School of Environmental Sciences. “Conservation gains from investing in a more hospitable matrix in agricultural and urban areas are far greater than previously realised.”

The study revealed that small forest patches retained significantly more bird species when surrounded by at least some tree cover rather than open water. Landscapes with greater surrounding tree cover supported richer bird communities overall. 

Lead author Anderson Bueno from the Instituto Federal de Educação, Ciência e Tecnologia Farroupilha, said: “Habitat remnant size is not the whole story. Two forest remnants of the same size can support very different numbers of bird species - those surrounded by farmland with nearby trees may host more than twice as many species as isolated remnants within reservoirs.”

Indeed, the study showed that even small amounts of tree cover within just 300m  of a forest remnant had a strong positive effect on species survival. Although the study was not done in Nepal, it has implications for buffer zones surrounding Tarai national parks where farms and urban buildup coexist.

Chase Mendenhall of Slippery Rock University hoped the study will support more effective land‑use policy and encourage governments and landowners to invest in wildlife‑friendly farming practices that support both biodiversity and agricultural productivity.

The findings highlight that, while protecting remaining forests is essential, restoring and improving the landscapes around them is also important. Planting native trees, restoring degraded vegetation, and creating wildlife-friendly agricultural land can dramatically reduce local extinction risks.

Human-modified landscapes now cover more than half of Earth’s land surface, increasing the significance of this study. The research team included 58 scientists from 19 countries to analyse results from 50 landscape-scale bird surveys across tropical and subtropical regions in the Americas, Africa, and Asia where natural landscapes have been heavily fragmented.

The unique design of the study compared two types of forest remnants: forest islands created by hydroelectric reservoirs, which represent the most extreme habitat fragmentation on Earth, and forest fragments embedded within terrestrial landscapes, often surrounded by agricultural land.

By comparing these contrasting systems, the researchers could quantify how much a more benign, tree-rich matrix can buffer species against local extinctions. More than 1,000 forest remnants were studies where almost 2,000 bird species were recorded, including critically endangered species.

The report in Proceedings of the National Academy of Sciences is titled ‘High-quality surrounding landscapes mitigate avian extirpations from forest remnants’.