Highways are being paved, oil is being drilled and entire cities are sprouting up inside many of the world's nature preserves, imperiling the very creatures they are meant to protect, researchers said Thursday.
The vast harm being wreaked by people inside protected areas that are home to endangered animals like the eastern black rhinoceros, Sumatran tiger and spectacled hare-wallaby was detailed in the journal Science.
One third of the world's protected areas are under "intense human pressure," warned the report.
Furthermore, some 2.3 million square miles (six million square kilometers) of protected land -- equivalent to two-thirds the size of China -- are unlikely to conserve endangered biodiversity.
"Only 10 percent of lands were completely free of human activity, but most of these regions are in remote areas of high-latitude nations, such as Russia and Canada," it said.
The problem is most acute in Asia, Europe and Africa, study co-author James Watson, director of the science and research initiative at the Wildlife Conservation Society, told AFP.
"Most nations are doing the first step, and gazetting protected areas but not doing the harder, and more important, second step of funding the management of those protected areas and ensuring they were secured against large-scale human interference," he said.
Protected areas are seen as a critical solution to the biodiversity crisis facing the planet, by allowing safe havens for birds, mammals, and marine life to thrive.
The amount of lands set aside globally as protected areas has doubled since 1992.
"We know that when they are well managed, well financed and well placed, they work," Watson said.
- Six-lane highway? -
But researchers found disturbing examples of large-scale human infrastructure being built inside nature preserves.
For example, railways run through Tsavo East and Tsavo West national parks in Kenya, home to the endangered eastern black rhinoceros and lion populations famous for their strange lack of manes, Watson said.
"Plans to add a six-lane highway alongside the railway are well underway," he said.
Barrow Island National Park in Western Australia -- home to endangered mammal species such as the spectacled hare-wallaby, burrowing bettong, golden bandicoot and black-flanked rock-wallaby -- also house major oil and gas extraction activities.
In the Indonesian island of Sumatra, more than 100,000 people have illegally settled in Bukit Barisan Selatan National Park -- home to the critically endangered Sumatran tiger, orangutan and rhinoceros -- and converted around 15 percent of the park area for coffee plantations.
US national parks like Yosemite and Yellowstone also suffer due to "the increasingly sophisticated tourism infrastructure being built inside their borders," he said.
"We found major road infrastructure such as highways, industrial agriculture, and even entire cities occurring inside the boundaries of places supposed to be set aside for nature conservation," said co-author Kendall Jones, a researcher at Queensland University in Australia.
"More than 90 percent of protected areas, such as national parks and nature reserves, showed some signs of damaging human activities."
Researchers said solutions include making sure governments set aside the funds to manage preserves strictly for biodiversity.
Some of the success stories in this realm include Keo Seima Wildlife Sanctuary in Cambodia, Madidi National Park in Bolivia, and Yasuni Biosphere Reserve in Ecuador, Watson said.
For example, railways run through Tsavo East (seen in 2016) and Tsavo West national parks in Kenya, home to the endangered eastern black rhinoceros and lion populations famous for their strange lack of manes