Peter Raven is a botanist. He knows about photosynthesis, primary productivity and sustainable growth. He knows that all flesh is grass; that the richest humans and the hungriest alike depend ultimately on plants for food, fuel, clothing, medicines and shelter, and that all of these come from the kiss of the sun on warm moist soils, to quicken growth and ripen grain.
The global population is about to soar from six billion to nine billion in less than a lifetime. Around 800 million humans are starving, and maybe two billion are malnourished, while three billion survive on two dollars a day.
By many, Raven means perhaps half to two-thirds of all the other species on the planet in the next 100 years. There could be ten million different kinds of ferns, fungi, flowering plants, arthropods, amphibians, reptiles, birds, fish and mammals on Earth. Nobody knows. People such as Raven, director of the Missouri Botanic Gardens in St Louis, are doing their best to count and preserve them.
Some of these organisms are now being chased to oblivion by human population growth at levels that ecosystems cannot sustain.
There are ways of confirming species loss, even if it cannot be established how many species there were in the first place. Look at the vertebrates and molluscs in fossil records, Raven says, just for the past sixty-five million years or so. “You find that the average life of a species is two to three million years and you get about one species per million becoming extinct per year in the fossil record. Those particular groups are a small sample, but they are a real sample,’ he says.
That works out at hundreds of creatures per year over the past four centuries, and even more, when humans, rats and other invaders started colonising islands: 2,000 species have vanished from the Pacific basin alone since the Polynesians got there 1,200 years ago.
There are various wild creatures that get along with humans and follow them everywhere: cockroaches, fleas, ticks, rats, cats, pigs, cattle, scavenger birds, and lusty weeds. These invade little islands of ancient biodiversity, take over, and see the natives off the premises. And not just islands: one-third of all endangered plants in the continental US are threatened because of alien invaders, Raven says. In Hawaii, it is 100 percent.
Ecosystems are not static. They change, naturally. They burn, are grazed or browsed, they regenerate, flood and silt up. But left to themselves, they go on providing services that humans and other creatures value. A mangrove swamp provides a habitat for shrimps. It cannot be improved by draining it for a tourist beach or building a large city on it. Its natural value would be dissipated. ‘An ecosystem itself undamaged is very, very resilient, and the more simplified it gets, the less resilient. Globally, what we are doing is simplifying them all, simultaneously, which is a very dangerous large-scale experiment,’ Raven says