Human activity continues to inflict widespread disruption on habitats all over the world, impacting biodiversity and leading to extirpation, if not extinction.
Now, the scale of its effect on wildlife down to the detail of individual vertebrate species has been mapped globally for the first time by Canadian, US, and Australian researchers.
Previous work has mapped where threats exist, but, according to the paper, none accounted for the “distribution and sensitivity of species and their threats and therefore do not directly map likely human impacts.”
Almost 1 in 4 species threatened across over 90% of their habitat
The habitats of 5,457 birds, amphibians, and mammals were examined as part of the study. The species were selected from the International Union for the Conservation of Nature’s list of threatened, vulnerable, and endangered creatures.
Eight of the most dangerous forms of human activity were included in the assessment — transportation networks, population density, urbanization, and farmland all being examples. Across 30 x 30 km grids, these threats were cross-compared with individual species to determine what the effects are.
For any individual species, there is a limit to the total range of their habitat; certain environmental conditions are needed to survive and thrive. Because these needs vary from creature to creature, some are confined to specific areas, while others are spread out far and wide (like migrating birds). Despite this, having your kin spread across a greater distance could still mean you can run but can’t hide, as researchers found that 84% of the Earth’s land has at least one of these threats present.
For one-quarter of all the species studied, this intensity of human coverage meant that over 90% of their habitat was threatened. A small minority of species (7%) were found to be threatened across the entire range of their habitat, including many “charismatic large mammals” such as tigers and elephants.
“We only mapped threats within a species’ location if those threats are known to specifically endanger the species,” says the University of Queensland’s James Allan, lead author of the study. “This means species will decline, and possibly die out, in the impacted parts of their habitat without conservation action. Completely impacted species will almost certainly face extinction.”
‘Hotspots’, ‘coolspots’, and what they mean for species caught up in them
Researchers identified ‘hotspots’ where the situation is particularly dire and ‘coolspots’ which are akin to refuges from the destruction. Tropical and sub-tropical areas like Southern Brazil, Indonesia, Thailand, and Myanmar were among the most heavily affected, and South-east Asia is home to the top five most-affected countries in the study.
On the positive side, around a third of the species were not affected by any of the eight major threats, although the team notes they may still be in danger of lesser threats not examined in the study. Large concentrations of unaffected species’ populations were found in the coolspots, which typically encompass relatively isolated places like the Arctic Tundra, yet confusingly, some of them overlap with the hotspots, as seen with Indonesia.
As explained by the authors, this is because these regions have an enormous amount of biodiversity to begin with, and threats that may be catastrophic for one species may be irrelevant to another. As an example, a small mammal might be affected by some form of construction blocking access to a vital resource, while a bird in the same area could simply fly over the obstruction.
Allan commented that areas that overlap like this offer a unique opportunity to pursue a two-pronged approach with conservation — that is, bolstering protection of those sheltered in the coolspot while actively working to dismantle threats that make the area a simultaneous hotspot for others.
The team hopes their work will better inform conservation and development efforts at a national and international level. Co-author James Watson commented that all of the threats could be stopped by conservation action (groundbreaking research published last year provided strong evidence for its long-term efficacy) and that all that is lacking is the political will and funding to pursue it.
“We have shown, throughout the world, that actively tackling these types of threats works, with species bouncing back when conservation action is targeted and well-resourced,” says Watson. “One obvious step is to proactively secure species’ threat-free refuges, which are paramount for their survival, avoiding any initial human impacts in these places.”