Ecosystems / LIFE
Planet Earth is home to an astonishing variety of life, from bacteria that live in the extreme heat of volcanic lava to ice-cap dwelling polar bears, from city-based humans to luminous fish in deep ocean trenches. All are interconnected in a fragile web of life called ‘biodiversity’.
Life on earth first evolved in the oceans over 2.5 billion years ago. Perhaps half a million years ago, one species of primate became more and more successful, and humanity spread throughout the world. By 10,000 years ago we were domesticating plants and animals; and by the 20th century our high-energy technologies and productive activities meant we were capable of the total transformation of ecosystems, something unprecedented in history.
The number of species threatened with extinction is a clear indicator of the state of the world’s ecosystems. Extinction means the death of birth. Five mass extinctions have happened in the past 500 million years. The sixth and greatest extinction in the history of our planet is happening today. It is almost entirely due to human activity, and is faster than any in history: we are losing species at a rate of up to 1,000 times the natural rate of extinction. Between a third and a half of terrestrial species are expected to die out over the next two centuries if current trends continue unchecked.
Humanity’s threats to biodiversity are manifold, from habitat loss to destruction of grasslands and forests, from overfishing, pollution and contamination to global climate change. The inter-relatedness of ecosystems means that a small loss in one area can affect many other species around it: for example, the decline of the honeybee leaves many fruit crops and flowers unpollinated. For in nature, diversity breeds diversity: trees in turn provide homes and food for birds, insects, other plants and animals and fungi.
This interrelatedness of all beings includes us. Human beings rely directly on the planet’s biodiversity for food, shelter and health; and indirectly for clean water, pure air and fertile soils. The lesson we need to learn urgently is this: we cannot do without the rest of the planet’s biodiversity, but it can do very well without us.
LIFE – THE FACTS
• Some 23% of mammal species, 12% of bird species and 32% of amphibian species are threatened with extinction.
• Over the past few hundred years, humans have increased the species extinction rate by as much as 1,000 times the background rates typical over the planet’s history.
• In some sea areas the total weight of fish available to be captured is less than a hundredth of that caught before the onset of industrial fishing.
• The distribution of species on Earth is becoming more homogenous. For example, a high proportion of the 100 or so non-native species in the Baltic Sea are native to the North American Great Lakes, while 75% of the 175 recently arrived species in the Great Lakes are native to the Baltic.
Source: Millennium Ecosystem Assessment 2005
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