Biodiversity, the diversity of life on earth, is essential to the healthy functioning of ecosystems. Habitat loss and overexploitation, driven by our rapid population growth, are the primary causes of species extinction which is now happening up to a thousand times faster than for millions of years before.
"We are in a bottleneck of overpopulation and wasteful consumption that could push half of Earth’s species to extinction in this century."
– E.O. Wilson
Diversity is key
Ecosystems, interdependent webs of living organisms and their physical environment, are vital to all life on earth. Our ecosystems provide us with clean air, fresh water, food, resources and medicine. Throughout earth’s history, healthy ecosystems have usually been resilient enough to adapt to gradual environmental change. Existing species may evolve or new species move in, in response to small changes in the habitat without collapse of the entire system.
Biodiversity, the range and variation of life in an ecosystem, is a major factor in its resilience. In a biodiverse ecosystem, if the environment changes and some organisms can no longer thrive, others can take their place and fulfill essential functions. It is often the most overlooked species that are the most important to healthy ecosystems. Insects, for example, play an essential role in pollinating flowering plants—a third of the food we eat depends on animal pollinators.
The Sixth Mass Extinction
Since life appeared on earth, there have been several mass extinctions in which many of the earth’s species were wiped out because of climate change, volcanic activity, the impact of an asteroid or reasons we have not yet discovered.
The plants and animals which currently live on Earth have continued to evolve over the 65 million years since the last mass extinction. But many scientists consider the huge reduction in biodiversity since the emergence of humans is now on the scale of another mass extinction. This is known as the Anthropocene extinction or sixth mass extinction.
WWF's latest Living Planet Report estimates that we have lost more than half of all vertebrate wildlife populations since 1970 and a German study found that flying insect populations (including pollinators) have crashed by three-quarters since 1989, likely reflecting similar trends around the world.
According to the IUCN Red List of Threatened Species, 41% of amphibians, 25% of mammals, 34% of conifers, 13% of birds, 31% of sharks and rays, 33% of reef-building corals, and 27% of crustaceans are threatened with extinction.
Some countries are worse off than others. The 2016 State of Nature report concluded that the United Kingdom was one of the most nature-depleted countries in the world.
Biodiversity loss is attributable to several causes, all of them driven by rapid human population growth and our unsustainable consumption.
Ever more people need ever more space. Human activity continues to encroach on natural environments, thereby destroying the habitats of countless species. While some progress has been made in slowing the rate of loss of tropical forests and mangroves, serious declines are also being seen worldwide in freshwater wetlands, sea ice habitats, salt marshes, coral reefs, seagrass beds and shellfish reefs. As our numbers rise, cities and industrial areas are growing and merging into each other, fragmenting the remaining habitat and leaving isolated “islands” of natural populations of plants and animals too small to survive.
Ever more people need ever more things. Humankind’s relentless consumption of resources such as timber, oil and minerals is continuing to destroy natural habitats around the globe. We are also putting enormous pressure on populations of wild species, both by bushmeat hunting in the developing world and by large-scale industrial fishing in our seas. Wildlife poaching and trafficking still present a huge threat to many species, including rhinos, tigers and pangolins.
Ever more people need ever more food. In order to meet the unsustainable consumption patterns of the developed world and feed the numbers of people living on the Earth today, humanity has developed agricultural systems which rely on monocultures, artificial fertilisers and pesticides. Monocultures are increasingly susceptible to disease whilst widespread pesticide use destroys insect populations indiscriminately. In addition, the growing pressure on food supplies means an increasing proportion of agricultural land is farmed intensively, with fewer off seasons or fallow years in which to recover. Currently, livestock farming contributes to more climate emissions than the entire transport sector and is the biggest cause of deforestation. Runoff from farms pollutes water bodies and causes harmful algal blooms and the collapse of fish stocks.
Ever more people produce ever more climate emissions. Our planet is on the verge of a climate crisis due to our endless production of greenhouse gases including carbon dioxide and methane. We are headed for a 3°C warmer world by the end of the century if we do not step up action on climate change. We are already seeing species decline due to global temperature increase. Every half a degree of warming has a huge knock-on effect on ecosystems, with mobile species running out of areas to migrate to and temperature-sensitive organisms like corals undergoing massive die-offs. When keystone species like reef-building corals disappear, the rich and complex ecosystems they support collapse as well.
Ever more people produce ever more waste and pollution. Our oceans are becoming choked with plastic waste which is killing millions of animals, from sea turtles to whales. The Ellen MacArthur Foundation estimates that by 2050, there will be more plastic than fish in the sea. As populations increase, the disposal of waste, in particular hazardous waste, becomes an increasingly serious issue. As well as affecting the lives of humans, noise, light and chemical pollution can disrupt wildlife behaviour. Light from human activities makes it harder for predator species to catch their prey. Noise pollution interrupts both hunting and mating signals in many species, disturbing natural behaviour.
Ever more people means ever more travel. Human travel across the world has a very large emissions footprint but it has also allowed the spread of invasive species, both accidental and intentional. As a consequence of the introduction of non-native species to some areas, such as rabbits and cats in Australia, goats on St. Helena, and American mink in Great Britain, we have put many vulnerable ecosystems at risk, threatening native species and diminishing biodiversity.
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Welcome to the Anthropocene - the age in which the main force altering the planet is us.
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