Quaint cobblestone towns and green pastures dot the Pyrenees Mountains, at the gates of Catalonia’s Aigüestortes i Estany de Sant Maurici National Park. Hike a few miles into the park, though, and the Spanish landscape of trickling rivers and montane meadows looks relatively untouched by people. Visit almost any national park, and it’s a similar story, with tourist towns, farms, and other development lapping at the edges of conserved lands. But just how much does the landscape change at these fringes over time compared with the protected areas?

Quite a lot, as it turns out. A recent study in PLOS One is the first to quantify the extent of change inside and outside of protected areas at the continental scale across Europe. Change at the edges is twice that inside the protected zones themselves, according to the study.

“It’s a huge difference,” says coauthor Niels Hellwig, a physical geographer at Potsdam University and Osnabrück University of Applied Sciences, both in Germany. The difference matters because habitats and ecosystems rarely end at the designated boundaries of conserved land, instead spilling out into the surrounding areas. If those surrounding zones change too much through logging or urbanization, for example, Hellwig says “these changes may affect the integrity of the protected areas, due to the ecological interactions.”

Governments often conserve land to maintain its ecological integrity. Conservationists already knew that protected areas, and particularly the zones around them, undergo some land cover change that can affect biodiversity and ecological function—whether forest loss, intensification of agriculture, urbanization, or the opposite: reforestation and a reduction in agricultural pressures.

The continental scope of the study, which the researchers break into multiple spatial scales, allows policymakers at many different levels to grasp changes around their protected zones, says ecologist Andrew Hansen of Montana State University in Bozeman, who was not involved with the new work. “It’s the sort of information that’s very highly relevant to managing a particular place,” he says.

Hellwig and his colleagues analyzed geospatial data from satellite images captured by Europe’s Copernicus Land Monitoring Service between 2000 and 2012. They looked at urbanization, intensification of agriculture, reduction of agriculture, forest gain, forest loss, and formation of water bodies as indicators of land cover change. They found that just 1.5% of European protected areas were affected by land cover change, compared to 3% of the 1-km-wide buffer areas encircling these conservation zones. Trends vary by region and by country, but in general, forest gain and loss are the main processes in play across Europe.

The study can’t say whether forest gain and loss are caused by humans or by natural processes, such as wildfire, Hansen notes. Hellwig acknowledges such limitations, while pointing out that the real value of the study is in quantifying the whole picture of land cover change.

To decipher what caused these patterns of change, the researchers employed statistical analysis that took into account climatic factors, such as change in temperature, and socioeconomic factors, such as travel time to cities and population density. In general, the most important drivers of land cover change were population density and traveling distance to cities, as well as latitude and longitude, which were treated as proxies for Europe’s north-to-south climatic gradient and east-to-west economic gradient.

Hellwig says studies like his point to the need for more research on the ecological processes happening in buffer zones and the role they play in park biodiversity. Forecasting change is another important future application, Hansen says.

Remote sensing scientist Matthew Hansen of the University of Maryland in College Park (no relation to Andrew Hansen) suggests studies like this underscore the need for “secondary status” lands on the fringes of protected areas, where development may need to be restricted. Quantifying land cover change has implications for sustaining ecosystems and the services they provide. “It’s a big deal globally,” he adds. “The more papers like this, the better.”