Episode 7 of Sir David Attenborough's latest series Planet Earth III is all about humans - and the impact they have had on the natural world.
The human world, from our cities to our fields, has spread to every corner of the globe. Wildlife now has to adapt to a vastly altered landscape…and contend directly with us.
Some animals are meeting this challenge head on. In Bali, long-tailed macaques have learned that by stealing tourists’ most precious items, they can barter for their favourite food. The older males won’t give you back your phone unless they get what they’re after.
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For many animals living alongside us, it pays to keep a low profile. Tawny frogmouths are masters of camouflage, and in Melbourne, Australia, they are preyed on by cats. Nevertheless, frogmouths are doing well here because the streetlights help them find their prey, and in many parts of the city they are now found in a higher density than in the surrounding countryside.
Some animals are so bold they don’t even try to hide. Rhinos walk through the streets of Sauraha, Nepal, simply to get to food on the other side of town. In Lake Tahoe, USA, black bears head to the city dumpsters in search of food before hibernation, and the rich food they find means that they are up to 50% heavier than their country-dwelling cousins.
For wildlife, part of the challenge is to keep up with us. Pavement ants are the most common ant in New York City, outnumbering New Yorkers by 1,000 to one. The secret to their success is their digestive system, which has been able to keep pace with the constantly changing human diet; 90% of what they eat now comes from human food. On Broadway Avenue alone they eat the equivalent of 60,000 hotdogs a year.
Life is not so straightforward for animals that are feared or persecuted by humans. Snake bites cause an estimated 60,000 human deaths every year in India alone, but in one Indian village, venomous cobras are seen hunting inside peoples’ houses. Remarkably, scientists believe that this coexistence has led to a change in the snakes’ behaviour; they move more slowly and are less likely to strike when disturbed.
However, when animals come into the human world to compete for resources, it often leads to conflict. In Kenya, once the sun has set, African elephant bulls venture to fields of tomatoes to gorge. It’s a dangerous job for the farmers trying to repel the largest land animals on the planet.
Surprisingly, wildlife eating the same food as humans doesn’t always result in competition. Off the coast of Vancouver Island, humpback whales inhabit waters that have been overfished. You would think that their presence would reduce fish stocks even further, but astonishingly the opposite is thought to be happening.
Although some species are managing to thrive in the human world, in many parts our actions are putting unprecedented pressure on wildlife. Our fates, however, are closely intertwined. If the natural world is not protected, it could be devastating for all humans on earth. The major challenge will be re-imagining the way we live on this planet to find ways to protect all life on earth.