Lost Wilderness: Restoring both Habitat and Animal Species

Photo credit: Hannes Flo, CC BY 2.0.

By Roberta Attanasio, IEAM Blog Editor

A month after the death of Henry David Thoreau, The Atlantic published his 1862 essay “Walking,” which “extolled the virtues of immersing oneself in nature and lamented the inevitable encroachment of private ownership upon the wilderness.” It included Thoreau’s famous line “In wildness is the preservation of the world”—eight powerful words that played a major role in saving places such as Yosemite and Cape Cod from human-caused environmental destruction, inspiring the creation of the US National Parks system. Upon signing the US Wilderness Act in 1964, President Lyndon B. Johnson stated: “If future generations are to remember us with gratitude rather than contempt, we must leave them more than the miracles of technology. We must leave them a glimpse of the world as it was in the beginning, not just after we got through with it.”

Fast forward to 2021—a new study (published 15 April 2021) found that only between 2% and 3% of Earth’s terrestrial surface consists of ecologically intact ecosystems, an estimate 10 times lower than previous ones. 

Andrew Plumptre, lead author of the study, said: “We know intact habitat is increasingly being lost and the values of intact habitat have been demonstrated for both biodiversity and people, but this study found that much of what we consider as intact habitat is missing species that have been hunted by people, or lost because of invasive species or disease.”

For the study, Plumptre and his collaborators combined different global datasets to evaluate the ecological integrity of different regions and examined both human damage to habitats and loss of animal species. They found only fragments of wilderness that qualified as “functionally intact,” mostly in a limited number of regions—Congo and Amazon tropical forests, east Siberian and northern Canadian forests and tundra, and the Sahara. A key point here is that these areas overlap with territories managed by indigenous communities, which play a major role in maintaining the ecological integrity of these regions.


Satellite view of the greater San Francisco Bay area, California, showing numerous nature preserves surrounding dense urban areas and agricultural land. Photo credit: European Space Agency, CC BY-SA 2.0.

A study published in 2018 produced the first map of the planet’s intact ecosystems, mostly based on satellite images. It found that more than 77% of land (excluding Antarctica) had been modified by the direct effects of human activities. In addition, the authors observed that just 5 countries—Australia, the US, Brazil, Russia, and Canada—contained 70% of untouched wilderness areas. They pointed out that time is running out to safeguard the health of the planet and human well-being, and that wilderness areas are now the only places that contain mixes of species at near-natural levels of abundance. Therefore, these areas are important reservoirs of genetic information, acting as reference for efforts to re-populate degraded regions.

However, to map Earth’s remaining terrestrial wilderness, they used eight indicators of human pressures—built environments, crop lands, pasture lands, population density, nighttime lights, railways, major roadways, and navigable waterways—to identify wilderness areas (free from human pressures).

In contrast, Plumptre and his collaborators used a different approach. In addition to habitat intactness, they also assessed faunal intactness (no loss of animal species) and functional intactness (no loss of animal densities below a level that would affect the healthy functioning of an ecosystem). Despite their estimate that only 2-3% of Earth’s terrestrial surface consisted of ecologically intact ecosystems, the authors believe there is hope—up to 20% of the planet’s land surface could be restored to faunal intactness through the reintroduction of only a few species into the remaining intact habitat. Plumptre said: “The results show that it might be possible to increase the area with ecological intactness back to up to 20% through the targeted reintroductions of species that have been lost in areas where human impact is still low, provided the threats to their survival can be addressed and numbers rebuilt to a level where they fulfil their functional role.”

Examples of targeted reintroduction are forest elephants potentially reintroduced in areas of the Congo Basin where they have been extirpated, and reintroduction of some of the large ungulates—buffalo, giraffe, zebras, and so on—that were overhunted from much of Africa’s woodlands and savannas. Notably, reintroduction should be carried out in areas with low human footprint, following guidelines necessary to minimize disease risks and possible conflicts with people. 

Plumptre told The Guardian: “We’re in the UN decade of ecosystem restoration now, but it is focusing on degraded habitat. Let’s also think about restoring species so that we can try and build up these areas where we’ve got ecologically intact ecosystems.”

Florida panther (Puma concolor coryi), a subspecies of the mountain lion, in Everglades National Park, USA. Photo credit: Rodney Cammauf (NPS photo), public domain.

A well-known example of existing successful reintroduction is that of wolves into Yellowstone National Park, USA, which has been defined as “a remarkable, continuing ecological and social drama that has changed the way biologists think about predators and the animals they stalk.” The reintroduction has inspired similar wildlife experiments elsewhere, namely panthers in Florida, USA. Another well-known example is that of the Tasmanian Devils recently reintroduced into the Australian wild north of Sydney.

Plumptre said that intact habitats provide benefits to both wildlife and people and therefore should be a critical target in the negotiations for the post-2020 global biodiversity framework. The framework is a stepping stone towards the 2050 Vision of “Living in harmony with nature.”

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