The Biodiversity Crisis: Background information when reading Sentient

The Biodiversity Crisis

This article relates to Sentient

From the peacock mantis shrimp's remarkable ability to perceive polarized light to the orbweaver spider's time-tracking powers, Jackie Higgins' Sentient showcases the varied sensory powers of a wide range of animals, highlighting the rich diversity of life forms found across the natural world.

Yet as climate change intensifies and habitat loss accelerates due to human encroachment, that diversity is in critical decline, with species extinction rates higher than at any other time in human history. According to a 2019 United Nations report, about one million plant and animal species are at risk of extinction—many within decades. Indeed, if the current trajectory persists, up to one-third of all species could be wiped out within 50 years. One half of Earth's plant and animal species may face extinction by the end of the century.

So dire is the biodiversity crisis that scientists warn we may be on the cusp of a sixth mass extinction—defined as a period when roughly three-quarters of all species disappear within a relatively short span of geological time, such as when the dinosaurs became extinct some 65 million years ago. According to the fossil record, five previous mass extinctions have occurred in the past 540 million years, triggered by events such as asteroid impacts, volcanic eruptions or ice ages. This time, the cause would be us.

While humans account for a mere 0.01% of the planet's living creatures, we have altered three-quarters of Earth's ice-free land surface and degraded two-thirds of ocean areas. Since 1990, the planet has lost some 420 million hectares of forest—an area roughly the size of Libya. More than 85% of the world's wetlands have disappeared. From coral reefs and rainforests to grasslands and prairies, vital ecosystems across the globe are increasingly threatened by agricultural and industrial expansion, urban sprawl, overexploitation of natural resources, pollution and climate change.

As a result, mammals, fish, birds, reptiles and amphibians around the world have seen their population sizes decline by an average of 68% since 1970. A quarter of all mammal species are now under threat because of habitat loss and environmental degradation. Nearly one-third of freshwater fish face extinction. One-third of the world's insect species are endangered. That includes many of the essential pollinators we depend on for our crops.

Among the species increasingly at risk from human causes are several featured in Sentient, including the cheetah, whose unrivaled land speed, as Higgins explains, is linked to its extraordinary sense of balance. Virtually extinct in Asia, cheetah populations in Africa have been decimated by habitat destruction, poaching, illegal wildlife trafficking and climate change. In the wild, only about 7,000 now remain.

While not globally threatened, the great gray owl is an endangered species in California, where deforestation threatens the habitat and breeding grounds of this acoustically gifted bird. And also vulnerable is the duck-billed platypus—"one of nature's most unconventional creatures," as Higgins describes it. Over the past three decades, this zoological curiosity with the remarkable ability to detect electromagnetic fields underwater has lost more than 20% of its habitat, in large part due to land clearing and the effects of human-induced climate change. Researchers from Sydney's Centre for Ecosystem Science now warn that the unique egg-laying mammal, found only in Australia, may be on the path to extinction—like the nation's other iconic animal, the koala.

Adult male great gray owl (Canada). Photo by Peter K Burian (CC BY-SA 4.0)

Filed under Nature and the Environment

This "beyond the book article" relates to Sentient. It originally ran in March 2022 and has been updated for the November 2022 paperback edition. Go to magazine.