The Biggest Threats to Biodiversity? Guns. Nets. Bulldozers.

We tend to look at what’s threatening endangered species on an individual basis. The ivory trade is killing elephants. Illegal gold mining poisons wild camels. The addax’s worst enemy is trophy hunting. Panamanian golden frogs are battling chytrid fungus, walruses struggle against climate change, and snub-nosed monkeys flee deforestation. The list goes on.

But what happens when you zoom out and take a look at endangered species as a whole?

Just in time for the International Union for Conservation of Nature (IUCN) World Conservation Congress in Hawaii this week, a team of scientists has taken a closer look at the Red List, analyzing more than 8,000 species considered near threatened, threatened, endangered, and critically endangered. From sifakas and sea snakes to cacti and corals, the researchers scoured the database, cataloguing the most formidable threats for each plant and animal. The results, published August 10 in Nature, might surprise you.

Worldwide, war is putting the existence of 121 species in the balance. Another 61 could become extinct due to avalanches and landslides. Droughts besiege 347 more species.

But overall, the biggest issues looming over endangered species aren’t volcanoes or mining or even climate change. They’re “guns, nets, and bulldozers,” say the researchers. In other words, hunting, fishing, and habitat destruction in the name of farming.

The study found that 6,241 Red List species are afflicted by overhunting, overfishing, logging, and other forms of overexploitation. These include creatures like the Bioko drill (killed for food), the totoaba (fished and shipped around the world for its fish bladder), and the Bornean wren-babbler (at risk from unsustainable logging).

Farming, livestock, aquaculture, and other agricultural activities threaten another 5,407 species. The researchers point to the Fresno kangaroo rat and the African wild dog as examples of animals increasingly at risk from agriculture—either by farmers plowing over natural habitat or ranchers killing predators as a way of protecting their livestock. 

These problems, of course, are larger than their impacts on any one species. Each year, deforestation claims enough trees to cover Panama. Around 85 percent of the world’s commercial fish populations are thought to be overfished, and tuna, marlin, and shark populations are at just 10 percent of where they were before the Industrial Revolution. Meanwhile, the illegal wildlife trade is worth an estimated $8 billion a year—and that’s not even counting the black market for timber and fish.

Perhaps most concerning is that more than 80 percent of the world’s endangered species are being killed by more than one thing. Threats to biodiversity often weave dangerous webs of interconnections. For instance, roads, railways, and service lines imperil more than 700 species outright via collisions, but they are also barriers that carve up habitat, which impedes genetic diversity. Additionally, these thoroughfares can provide easy access for poachers seeking fresh hunting grounds, and they truck in pollution, irresponsible tourists, and soldiers.

“Unfortunately, we're only beginning to understand the ecological outcomes of threat interaction,” says lead author Sean Maxwell, a conservation scientist at Australia’s University of Queensland.

Here’s a list of some of the outcomes Maxwell says we do know about: Lions are more susceptible to disease during a drought; deforestation is more likely when new roads make forests more accessible; inappropriate fire management can facilitate the spread of invasive species; and oil and gas infrastructure can make seemingly forested landscapes uninhabitable for birds. You could say the troubles the world’s most beleaguered species face are as intertwined as the ecosystems these animals and plants call home.

If there’s one thing amiss about the research, it’s that the study sample of 8,000 or Red List species does not represent a random assortment of endangered life on earth. The study highlights plants and animals that scientists have, for one reason or another, had an occasion to study. That means thousands of species aren’t being taken into account here—either from lack of research or the fact they haven’t been discovered yet. Just look at fungi, say the authors: The extinction risk has only been calculated for 0.1 percent of the 50,000 species we think might be out there. 50,000!

It’s also true that threats to biodiversity can change and intensify over just a few decades. The United Nations estimates that the world population will grow to 9.7 billion by the year 2050. More people will bring more farming, more tree clearing, and more hunting, fishing, and trapping. And let’s not forget climate change. “There's very little we can do inside conservation areas to stop temperatures and sea levels from rising, or from droughts and storm surge events from becoming more intense,” Maxwell says. 

But survival is often a numbers game, and species with more robust populations will have a better shot at enduring or evolving in an era of climate change. So addressing the more immediate issues of overhunting, overfishing, and overdevelopment is more important than ever. “Stronger enforcement of old-growth forest logging regulations, for example, will help species currently threatened by logging but will also help them move away from unsuitable changes in climate in the future,” Maxwell says.

Likewise, areas with greater biodiversity are better able to withstand change of any kind. Larger stands of habitat allow for more genetic mixing, giving rise to the mutations that allow species to adapt. Not to mention, healthier ecosystems are better at storing carbon than a cornfield or grazing pasture, so keeping habitats intact will also help mitigate climate change in the long run. You see, solutions can be interwoven, too.

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