Extinction is forever

The Living Planet Report 2016 – risk and resilience in the new era

by Stan Hirst

4ff8753daf761f70af20b5e0c0ed9b0cExtinction is one of those words in the English language which seem distant and not particularly relevant to anything until you grasp the context. For me the significance of the term came on a hot summer day more than 60 years ago when my high school class shuffled obediently through the musty halls of the Transvaal Museum in Pretoria, South Africa.  We stopped in front of one ancient cupboard from which the museum guide brought forth a yellowing and battered skull, no jawbone attached.  It looked like a horse or a donkey, but Mr Naudé proudly advised it was the skull of a quagga which had once roamed the barren plains of the Karoo. We were sombrely reminded that the quagga had been extinct since 1885.

Gone forever, extinct not just in the Karoo or just in southern Africa, but everywhere in the world. Hunted to extinction because they were considered by farmers to be expendable and a damned nuisance, competitors with their sheep and cattle for scarce grazing, and good for nothing except maybe for the hides which made passable thongs for stock whips.

Extinction seemed profound to me at the time but it has always been passé for Earth. Over the past 500 million years there have been five major periods of mass earth wide extinctions, each one linked to profound changes in climate.  The Cretaceous mass extinction 65 million years ago is famously associated with the demise of the dinosaurs. Virtually no large land animals survived, while plants were greatly affected and tropical marine life decimated.

Now we’re well into the sixth extinction which has garnered the name Anthropocene extinction because of the strong causal links to human activity.  At least 875 extinctions of whole families of plants and animals  – mammals, birds, amphibians, reptiles and arthropods – have been documented to date by the International Union for Conservation of Nature and Natural Resources.  The rate of extinction has been roughly estimated at something like 140,000 species per year, making it the greatest loss of biodiversity since the Cretaceous extinctions.

lpr-coverScientists have been warning for decades that human actions are pushing life toward a sixth mass extinction, and more evidence comes from the recent 2016 Living Planet Report. This report documents how wildlife populations have declined, on average, by 67 per cent over the past decade, mainly the result of rampant poaching and wildlife trafficking.

The Anthropocene climate is changing rapidly, oceans are acidifying and entire biomes are disappearing – all at rates measurable during a single human lifetime. The future of many living organisms is now in question. Not only are wild plants and animals at risk, we ourselves are now the victims of the deteriorating state of nature. Climate and other predictive models indicate that, without decisive action, the Earth is on its way to becoming considerably less hospitable to modern globalized society.

global-living-planet-indexThe Living Planet Index (LPI) is a measure of biodiversity.  It draws on population data from 14,000 monitored populations of 3,700 vertebrate species (mammals, birds, fishes, amphibians, reptiles) around the world and then calculates an average change in abundance over time.  From 1970 to 2012 the LPI showed a 58 per cent overall decline in vertebrate population abundance. That means that global vertebrate populations have, on average, dropped by more than 50% in little more than 40 years.

Five threats show up consistently as the causes of wildlife population declines:

comp-fig

The most common threat to declining terrestrial populations is the loss and degradation of habitat, followed by overexploitation by humans. For marine species overexploitation is the main impacting factor, followed by loss and degradation of marine habitats.

wordl-populationWe have strained the limits of natural resilience all the way to the planetary level. The world’s population has grown from about 1.6 billion people in 1900 to today’s 7.3 billion.

In the early 1900s an industrial method was developed for fixing nitrogen into ammonia; the resulting synthetic fertilizers now sustain more than half of the world’s population, but at the same time causing massive pollution of air, water and soils. Fossil fuels incur tremendous costs in terms of rising atmospheric CO2 concentrations and resultant global climate change. (Figure C)

Since the early 1970s we have been demanding much more than the planet can sustainably provide. By 2012, the biocapacity equivalent of 1.6 Earths was needed to provide the natural resources and services we humans consumed in that year. Exceeding the Earth’s biocapacity to such a degree is simply not possible in the long term. We cannot cut trees faster than they mature, harvest more fish than the oceans can replenish, or emit more carbon into the atmosphere than the forests and oceans can absorb. The consequences of this “overshoot” are already abundantly clear everywhere.

How can we change the course of socio-economic development onto a pathway that does not conflict with the welfare of the biosphere? How can we begin to affect development in a way that will make essential changes at a relevant magnitude?

We’d better decide fast.  In the time it took to read this post one more species somewhere on Earth – maybe a plant, an  insect, a fungus, a bird, a fish, a marine invertebrate  or maybe a mammal, went extinct.

 

 

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