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Jaguars are carnivorous mammals in the cat family. They are the largest species of cat in America and can weigh up to 150 kilograms.

Humans affect wildlife even in protected areas

“We have evidence that animals are affected by what is happening both inside and outside of the protected areas,” researcher says. 

The Earth’s wilderness areas are disappearing rapidly. Tropical forests are under particularly intense pressure, with most of the world’s deforestation occurring there. 

The culprits are numerous: logging, agriculture, cattle ranching, mining, oil extraction, and dam construction. As habitats disappear, wildlife and biodiversity are impacted negatively. In addition, animals in tropical forests are often subjected to hunting.

Protection is inadequate

“Living inside protected areas may not automatically protect tropical mammals from the effects of human activities,” Asunción Semper-Pascual says. She is a researcher at the Norwegian University of Life Sciences (NMBU).

Protected areas are meant to be wildlife sanctuaries and provide protection for biodiversity. However, this protection can be flawed.

A new study led by NMBU challenges the idea that protected areas are 'undisturbed’ and a place where animals can live completely unaffected by humans.

Researcher Asunción Semper-Pascual.

“We have evidence that animals are affected by both what is happening inside and outside of the protected areas,” she says.

The largest study of its kind

The results from the study are based on one of the largest long-term standardised camera-trap wildlife surveys to date. The researchers have used millions of camera images to examine how human activities affect 159 mammal species in 16 protected areas in tropical regions across three continents. 

The images were collected over a decade from over 1,000 areas in tropical forests.

“All images have been collected using the same methodology,” Semper-Pascual explains. “Thus, making comparisons across sites and regions much more robust.”

Protected areas in the study include Bwindi Impenetrable National Park in Africa, Yasuni National Park in South America, and Pasoh Forest Reserve in Southeast Asia, to name a few. 

Examples of animals captured on camera include species such as the jaguar, the mountain gorilla, and the Sunda Pangolin.

Some are more vulnerable than others

The researchers found differences between animal groups with regards to susceptibility to human impacts and activities.

Specialist species are animals that rely on a specific habitats only. They thrive when the landscape is uniform and not fragmented. 

“These animals are generally more susceptible to the negative impacts of deforestation,” Semper-Pascual says.

On the other hand, generalists thrive in more diverse habitats where they have access to a greater variety of food and shelter.

The tayra is an omnivorous animal in the weasel family that inhabits South and Central America. Photo from Yasuni National Park in Ecuador.

“Habitats are more varied at the edge of a protected area,” she says.

In these edges, for example, the transition from dense forest to open agricultural landscapes offer a more diverse habitat than homogenous areas, such as deep within a forest.

More susceptible to human interference along the edges

However, animals living closer to the edge of the forest are more exposed to human activities such as hunting. The potential negative effects depend on human densities.

The benefits generalist species derive from living near the edge only outweigh the drawbacks if the nearby human population density is low.

“What we found is that when the human population density is high in these areas, then these species no longer benefit from being near the border, probably because of pressure from hunting or some other type of human interference,” Semper-Pascual says.

Only halfway to the goal of protecting areas

At the UN Biodiversity Conference in December 2022, participants agreed to designate 30 per cent of the Earth's land and ocean areas as protected areas by 2030. In 2020, approximately 17 per cent of the Earth's land areas were protected. 

“If we are to achieve the 30-by-30 goal, we need to double the coverage of protected areas within seven years,” Semper-Pascual says. 

The results of this study show that protection might not always work.

“As more protected areas are created, we need to think carefully about the factors both within and outside protected areas that influence biodiversity,” she says. “However, we have to think about the situation holistically. Conservation is going to work best when it’s tackled in specific contexts and in concert with the people who live there to create win-win situations for both the people and the wildlife.” 

About the project

The project is led by researchers from the Norwegian University of Life Sciences (NMBU) and Wageningen University & Research, and in close collaboration with Rice University (Texas, USA).

The wildlife images are collected by the Tropical Ecology Assessment and Monitoring Network, a joint effort by Conservation International, the Wildlife Conservation Society and the Smithsonian Institution

The Research Council of Norway (NFR301075) and the National Science Foundation (2213568) supported the research.


Semper-Pascual et al. 'Occurrence dynamics of mammals in protected tropical forests respond to human presence and activities', Nature Ecology and Evolution, 2023. (Summary)

Giant anteater - an insectivorous mammal native to Central and South America. (Video: Tropical Ecology Assessment and Monitoring Network)

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