The Unprecedented Presence of People Weighs on Wildlife

The International Union for Conservation of Nature classifies lions as vulnerable and estimates that only 23,000 remain in the wild. World Wildlife Fund states that while lions are not currently endangered, population numbers will continue to decrease without proper conservation efforts.

In our human-dominated world, Earth’s most iconic and imperiled wildlife are facing tough decisions. Two lion brothers recently illustrated that fact when they undertook a long, record-breaking swim across a predator-infested African river in search of homes and mates. Although there was a small bridge over the river, it’s thought the lions avoided it because of the presence of people.

Around the world, runaway human population growth is collapsing the role of wildlife in the world’s ecosystems. From deforestation to disease, from habitat fragmentation to lead poisonings, and from vehicle collisions to the wildlife trade, the human impact on wild animals is formidable.

What can we do to lessen our dominance and damage? Scientists say that conserving about half of the global land area could maintain nearly all of nature’s contributions to people (NCPs) and still meet biodiversity targets for tens of thousands of species. There’s work to do, however: most of the lands prioritized for NCPs are at risk of conflict with human development, with only 18% of that land area currently protected.

Queen Elizabeth National Park in Uganda is backed by the Rwenzori Mountains, also known as the “Mountains of the Moon” because of their snowcapped peaks. The park also provides visitors with stunning, panoramic views of crater lakes (such as the one above) carved into the green, rolling hills.

The literal lengths African lions will go to in order to avoid us

On February 1, 2024, a drone equipped with high-definition, heat-detection cameras captured some incredible footage. Two male lions were filmed in Uganda at night swimming across the Kazinga Channel, a waterway connecting Lake Edward and Lake George. The channel is a popular feature of the country’s Queen Elizabeth National Park.

The pair of big cats had previously been seen attempting to cross the channel three times before, but on each occasion, they were turned back to shore shortly after entering the water due to what appeared to be an animal trailing them—possibly a hippopotamus or a Nile crocodile. On the fourth attempt, the lions’ 0.62-mile crossing was successful.

Locally, the lions are known as “Jacob” and “Tibu.” Jacob has a harrowing history: some members of his family were poisoned for the lion body-part trade, he has been gored by a buffalo, he was caught in a poacher’s snare, and he lost one leg when it was caught in a second poacher’s steel trap. The population of lions that Jacob and Tibu belong to has nearly halved in just five years.

The fact that the two brothers have managed to survive as long as they have in a national park that has experienced significant human pressures and high poaching rates is a feat of resiliency, say the researchers who filmed the epic swim. Their paper on the topic was published in the science journal Ecology and Evolution on July 10, 2024.

Within Queen Elizabeth National Park is the Kazinga Channel. Its shores draw large numbers of wildlife, such as antelope, buffalo, crocodiles, elephants, hippos, waterbuck—and two daring lions.

But why did Jacob and Tibu risk the dangerous night crossing in the first place? Scientists theorize that the brothers were looking for females. Competition for lionesses in the park is fierce, and they had lost a fight for female affection in the hours leading up to the swim. So, it’s likely the duo mounted the risky journey to get to the females on the other side of the channel. There is a small connecting bridge to the other side, but the presence of people, say the researchers, was probably a deterrent.

The worst threat to wildlife across North America and Canada is us

Africa’s Jacob and Tibu aren’t the only animals floundering under the preponderance of people. Here, on the North American side of the planet, wildlife is feeling our weight, too.

In wildlife rehabilitation centers across Canada and the United States, licensed individuals and organizations take in hundreds of thousands of injured and sick wild animals every year. In fact, such centers see the highest number and greatest range of species of any government or nonprofit organization in the U.S., giving them unique insights into animal health—and making them great bellwethers of what’s happening in the broader environment.

Wildlife rehabilitation centers see the highest number and greatest range of species of any government or nonprofit organization in the U.S. This gives them a unique insight into animal health in the broader environment.

A few years ago, a biologist named Tara Miller, who was then working with Defenders of Wildlife, met Wendy Hall, cofounder of the Adirondack Wildlife Refuge in Wilmington, New York. Hall mentioned some weird occurrences she had noticed in her job over the last few years: black vultures in the Adirondacks, which was unusual since they are typically a southern species; and earlier “baby seasons” in many species, which researchers have linked to climate change. Miller was intrigued by the idea of using animals’ presence in rehab centers to study the impact of climate change and people on North America’s wildlife.

Miller is the lead author of a first-of-its-kind study, published in Biological Conservation in October 2023. The study compiled hundreds of thousands of records from 94 wildlife rehab centers across Canada and the United States to investigate the threats facing more than a thousand wildlife species by region, including which threats affect which animals and how effective these centers are at treating their patients.

In summer 2019, Miller began contacting employees of wildlife rehab centers, which varied in size from those rescuing a few hundred animals a year to groups helping tens of thousands. She asked what trends they had noticed and what questions they would like answered through a report.

Black vultures have been making their way north due to milder weather caused by climate change. Ornithologists in New York have recorded more than 300 sightings in the last year. That number would have been unheard of 30 years ago, say researchers.

Until recently, most wildlife rehab records existed only in binders and file cabinets, which made them inaccessible to researchers. But slowly, over the last decade or so, centers have started to digitize their documents, thanks in part to software such as the Wildlife Center of Virginia’s WILD-ONe patient database for wildlife rehabilitators. This gigantic dataset has more than 600,000 observations. The big question for Miller was, what are the major threats to wildlife?

The data revealed that 40% of animals were sent to rehab centers because of injuries classified under the “human disturbances” category. These included bald eagles sickened by lead poisoning, big brown bats colliding with buildings and sea turtles entangled in fishing gear.

Seasonally speaking, the researchers found vehicle collisions were highest from May to July and disproportionately affected reptiles. Pesticide poisonings increased in the spring, summer and early fall, a time of more agricultural and construction activity. Lead poisonings tended to be seen in the winter, after hunting season. Many hunters still use lead ammunition when deer hunting, which will then poison scavengers like bald eagles and vultures when they go in to snack on a carcass.

In addition, the investigation showed that more animals were admitted to wildlife rehab centers the week after extreme weather events than the week before—following floods and hurricanes in southern Florida, for example. More animals were also taken in after big storms in recent years, possibly due to the increasing intensity and frequency of extreme weather events.

Scientists say pelicans do well after rehabilitation; 68% of injured pelicans are later released back into the wild.

About one-third of the animals brought into wildlife rehab centers are eventually released back into the wild, though this number varies significantly among species. For example, about 68% of injured pelicans are later released, whereas only about 20% of bald eagles have that option.

These findings tie together what rehabbers across the country are seeing: the big picture of how humans are impacting wildlife. Miller says that we should be thinking about the issue in terms of disaster and response plans. Do we need to boost state funding to animal rehabilitation centers to be able to care for wildlife after catastrophic events? How can we change our behaviors and policies to impact animals less?

In the meantime, the results of this study can hopefully convince communities to make some fairly easy changes to protect animals. Wildlife underpasses and overpasses across roads can help deer, turtles and other animals cross highways safely (and reduce car accidents). Adding decals and other patterns to windows can save birds. And educating the public on how to phase out lead fishing gear and hunting ammunition can cut down on poisoning in scavengers. Some states have lead ammunition buyback programs, and more could establish them.

These changes will help humans, too: for example, car-deer collisions are not only expensive to fix but can be deadly for all parties.

Only about 20% of injured bald eagles that recover at rehabilitation centers, however, can be released. Scientists wonder why the full recovery chances are so different between bald eagles and pelicans.

The “Humpty-Dumpty effect” of us

Some of the world’s most spectacular and unheralded mammals are now slipping away, such as Bhutan’s takins, Patagonia’s huemuls, Tibet’s wild yaks and Vietnam’s saolas. Even Africa’s wildebeests and three species of zebras have suffered massive reductions over the last several decades.

The reasons for these losses are more than deforestation, disease, habitat fragmentation or the wildlife trade, according to researchers at Colorado State University and their colleagues around the world. Ultimately, the cause is rampant human population growth. And unless human behavior changes in unprecedented ways, states the research team, future communities of these mammals will never resemble those of the recent past or even today.

In 1830 when Vice Admiral Robert Fitzroy captained his ship, the HMS Beagle, through the Strait of Magellan at the southern tip of South America, fewer than 1.2 billion people inhabited Earth. By Earth Day in 1970, there were more than 3.5 billion. Today, slightly more than 50 years later, the world’s population exceeds 8 billion. Livestock and humans now constitute a staggering 97% of the planet’s mammal biomass.

Legend has it that Drukpa Kunley, a Bhutanese poet and yogi popularly known as “the Divine Madman,” combined the head of a goat with the body of a cow to create the takin, now Bhutan’s national animal. The takin’s conservation status is vulnerable.

In a report published in Frontiers in Ecology and Evolution in June 2020, the Colorado State University scientists described how they analyzed direct and indirect disruptions that lead to changing roles of mammals in global ecosystems. They noted how the nature of ecological interactions has changed and will continue to do so—on an even larger scale—in coming decades.

More specifically, the researchers looked at what has transpired with coyotes and wolves in North America, huemuls in Patagonia, takins in Bhutan, wild horses in deserts, and the inevitability of change in big ecosystems as humans extirpate large carnivores and increase their footprints on the land.

For example, humans have only recently colonized parts of the Himalayas, areas where ice has receded due to warming temperatures. But the scientists’ findings showed that even in the remote reaches of the Himalayas, feral and stray dogs—a direct result of human intrusions—wreak havoc on wild species that have high cultural importance and economic value.

Patagonian huemuls live in the rugged regions of the southern Andes. They are diurnal and have well-developed senses of hearing, smell and vision. When alarmed, huemuls snort and stamp their front legs. With less than 1,500 individuals left, they are listed as endangered.

Worldwide, food webs have become irretrievably altered by humans, with little hope to reconstitute even recent past conditions or to put back the ecological functions once created by native species. Feral pigs, for instance, exist today on every continent except Antarctica and in 70% of the states in the U.S. These animals disrupt birds, fish, reptiles other small mammals, plants and soils. In addition, human-caused climate change warms the oceans, which in turn foments marine algal blooms, reducing fishery catches. With less fish, a consequent uptick in wildlife poaching on land occurs.

The scientists also documented how an appetite for fashion like cashmere increases imports to the West from China, India and Mongolia, resulting in economic incentives for desert pastoralists to produce more domestic goats in central Asia. These goats compete with native species for food. And domestic dogs that pastoralists introduce are not only predators but also carriers of diseases that jeopardize endangered species, such as kiang (a large horse of the Tibetan Plateau), Przewalski’s gazelles and snow leopards.

Despite these grim findings, the study’s authors suggest that all is not yet lost. While for many assemblages of animals, we are nearing a moment in time when—like Humpty-Dumpty—we will not be able to put things back together again, the world still has some remarkable protected areas, including Kruger National Park and Serengeti National Park in Africa, the Patagonia Ice Fields of Argentina and Chile, Madidi National Park in Bolivia, Chang Tang Nature Reserve in China, Northeast Greenland National Park (the world’s largest national park), and Yellowstone National Park and Wrangell-St. Elias National Park and Preserve in North America.

We’re fortunate that the world still has some remarkable protected areas, such as Yellowstone National Park in the United States.

And although food webs with large mammals will be different from those of the past, there are options to shape the future. We need to use our ecological grief, say the authors, to implement action and honor the exceptional biodiversity that remains. This can be done by protecting large tracts of the planet’s wild places.

Only 18% of lands prioritized for nature’s contributions to us are protected

That brings me back to E. O. Wilson’s theory on conserving half of global land area in order to maintain nearly all of nature’s contributions to people (NCPs) and still meet biodiversity targets for tens of thousands of species. Even 30 x 30 would be a good start. Unfortunately, a new study, published in the journal Nature Communications in January 2024, shows that only 18% of lands prioritized for NCPs are protected.

This study, led by researchers at the Cornell Lab of Ornithology, is based on a global-scale optimization of land uses to identify joint priorities for biodiversity and NCPs. Focusing on regions of high conservation value that are also under high development pressure reveals some unlikely areas that don’t always garner global conservation attention; these include working landscapes in southeastern Australia, southern Brazil and Uruguay, Eurasia and the southeastern United States.

In the areas of commercial agriculture and renewable energy, more multifunctional landscape planning would be highly beneficial. One example of this is to allow livestock grazing on wind farms.

Findings showed that roughly half (44% to 49%) of global land area, excluding Antarctica, provides nearly all (90%) current levels of nature’s services to people while also conserving biodiversity for 27,000 species of amphibians, birds, mammals and reptiles. But the results also point to potential conflict, because 37% of the land areas are highly suitable for development by agriculture, renewable energy, oil and gas, mining or urban expansion. Such high development potential, coupled with the fact that few priority areas are currently protected, means that successful conservation will require creative solutions.

Such solutions will carefully accommodate human activities through sustainable use and multifunctional landscape planning, particularly in the growing areas of renewable energy and commercial agriculture. Examples of this include livestock grazing under the turbines of wind farms or cultivating native pollinator gardens under solar panels.

But there’s a real risk that achieving renewable energy goals could conflict with nature conservation goals. We now know that biodiversity, climate change and sustainable development cannot be considered in isolation. Nature’s many contributions to human well-being—including carbon storage, clean water, coastal protection, crop pollination and flood mitigation—must also be factored in.

Solar panels and pollinator gardens do mix! We can generate renewable energy while nurturing and protecting the natural world around us.

For as English writer Alan Watts wrote, “Just as there is an interdependence of flowers and bees, where there are no flowers there are no bees, and where there are no bees there are no flowers. They’re really one organism … . The essential point is obvious: that each one of us, not only human beings but every leaf, every weed, exists in the way it does, only because everything else around it does. The individual and the universe are inseparable.”

Here’s to finding your true places and natural habitats,

Candy

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