It’s a hard line, but it’s not visible. Where the Serengeti National Park in Tanzania borders the land of the people who live there, there is no fence. Transfers in both directions take place regularly. This is not only the case in Africa’s most well-known national park, but almost everywhere where protected areas meet inhabited and cultivated land.

In three recent studies, researchers have addressed the question of whether existing protected areas around the world can live up to their name and really protect the species found there and ensure their survival. Their results are unequivocal: If it is not possible not only to preserve ecologically intact areas, but also to enlarge them and connect them with others, many animal species will become extinct.

The biodiversity in today’s protected areas dates back to times when habitats were larger. Today, wild animals sometimes graze next to cattle on pastures, they occasionally plunder fields or kill domestic animals. Herders drive their cattle to graze in protected areas where they can transmit domestic diseases to wild animals, and poaching is a widespread problem. For the people it is about the fight against poverty, for the wild animals it is about survival.

Around half of the world’s land mammals (44 to 65 percent) could become extinct because the existing protected areas are not sufficient, report David Williams from the British University of Leeds and colleagues in the journal “PNAS”. Researchers anticipate that surrounding unprotected areas will continue to be ecologically degraded over the course of this century due to population growth and human use. The survival of many terrestrial vertebrates depends on protected areas.

However, the analysis of data from around 4,000 animal species shows that the protected areas are not sufficient for most of the species that are already threatened with extinction, but also for a third of the species that are not currently classified as threatened. Hundreds of species do not have long-term viable populations within secure boundaries. Williams and colleagues report that large mammals, endemic species with a small distribution area and animals in species-rich tropical regions are particularly threatened.

“Our results indicate that the global network of protected areas needs to be greatly expanded, especially to include protected areas in different regions that also contain species that are not currently protected,” the scientists write. In addition, each area would have to be large enough to ensure that the protected species can survive there in the long term.

A research team led by James Allan from the University of Amsterdam in the Netherlands has estimated the minimum area required to secure important biodiversity areas, ecologically intact areas and optimal distribution areas with many species and ecosystem types. As the team has now reported in the specialist magazine “Science”, around 64 million square kilometers of land would have to be placed under protection – that is 44 percent of the land area of ​​the earth.

People don’t always have to be locked out. Rather, measures could range from restrictions on use to strict protection. More than two-thirds of this area has so far been unclaimed. More than 1.8 billion people currently live in the remaining third. “Measures to promote autonomy, self-determination, equity and sustainable management to protect biodiversity are essential,” the authors write.

Modeling of future land use shows that 1.3 million square kilometers are likely to be transformed by humans within this decade, “which warrants immediate attention.” However, in optimistic scenarios, the area occupied is significantly less, showing that this crisis could be averted. The authors propose “appropriate targets” in global biodiversity protection. Retaining the areas designated in the study would make a significant contribution to protecting biological diversity.

The “Aichi” target 11, named after the Japanese conference location, was formulated as part of the United Nations Convention on Biological Diversity. Accordingly, by 2020 at least 17 percent of the earth’s land area should be protected. This goal was not achieved, and researchers consider it insufficient anyway.

“Conservation means allowing natural processes on sufficiently large areas,” said Valerie Köcke from the Frankfurt Zoological Society to the Tagesspiegel. Due to global warming, many species would no longer be able to survive in their current range. “We minimize the risk of further extinction events if we allow species to shift their distribution areas,” explains Köcke. Protected areas would have to provide sufficient space for such processes, or it would have to be created by corridors between protected areas.

A team led by Angela Brennan of the University of British Columbia in Canada has studied the connectivity of current protected areas around the world by modeling the movements of medium to large mammals. Scientists identified land areas that could connect existing protected areas, particularly in Eastern Europe and Central Africa.

The most important connecting routes are threatened by human intervention. For the functional linking of the protected areas, new, additional ones would have to be set up, but above all the use of the corridors by people would have to be made compatible. Both strategies together could maximize the benefit, write the researchers in the journal Science.

“However, this is only possible if there are no ‘hard edges’,” says Köcke. These are the boundaries between protected areas and heavily populated landscapes used by people. This is where human-wildlife conflicts occur as they compete for space and biological resources. “If protected areas cannot be surrounded by buffer zones with reduced land use, then intensive cooperation between nature conservation and the local communities is required,” says Köcke. This also includes supporting them in developing sustainable sources of income.