Weekend Argus (Saturday Edition)
Call to slow sixth mass extinction as species vanish
WITH their bright, blazing skin, Costa Rica’s golden toads were described as little “dazzling jewels” as they gathered to breed on the floor of the cloud forest of Monteverde.
After their discovery in the 1960s, population sizes of around 1 500 adults, who lived almost entirely in moist burrows underground, were recorded.
But by 1987, only 11 golden toads were spotted and in 1989, just one solitary male. Despite extensive searches, the enigmatic species had hurtled into oblivion and was later declared extinct.
“The symbol of the amphibian holocaust is the loss, soon after it was discovered, of the gorgeous golden toad,” write researchers from Stanford University and the National Autonomous University of Mexico in a new paper on the extinction crisis, published in the Proceedings of the National Academy of Sciences this week.
Their study, “Vertebrates on the Brink as Indicators of Biological Annihilation and the Sixth Mass Extinction”, warns how for the planet’s landbased animals, extinction rates are human-caused, accelerating and may be a tipping point for the collapse of civilisation.
Frogs and toads, say the authors, are the “champions” of recent, rapid species extinctions, with hundreds of species suffering population declines and extinctions. The principal culprit is the chytrid fungus, which is sometimes spread by human activities and affects populations weakened by climate disruption particularly rapidly.
Millions of animal and plant populations have vanished in the past century with most people unaware of their loss, write the researchers, yet such losses have become extremely severe in the last few decades.
“These losses are not simply happening to obscure organisms of little interest to anyone. Instead, they include many large and conspicuous animals and plants, from lions and tigers to elephants and cacti.”
The researchers examined 29400 species of terrestrial vertebrates and determined which are on the brink of extinction – those that have fewer than 1 000 individuals – finding 515 species are in this bleak category.
“Our results emphasise the extreme urgency of taking massive global actions to save humanity’s crucial life support systems,” they write.
Humanity needs the life support of a relatively stable climate, flows of fresh water, agricultural pest and disease vector control, pollination for crops – all provided by functional ecosystems, says the study.
“Around 94% of the populations of 77 mammal and bird species on the brink have been lost in the last century. Assuming all species on the brink have similar trends, more than 237000 populations of those species have vanished since 1900.”
The acceleration of the extinction crisis “is certain because of the still fast growth in human numbers and consumption rates”.
Species, too, are links in ecosystems, “and as they fall out, the species they interact with are likely to go also.
“The ongoing sixth mass extinction may be the most serious environmental threat to the persistence of civilisation, because it is irreversible”, say the researchers.
“It’s probably the most serious environmental problem because the loss of a species is permanent – each of them playing a greater or lesser role in the live systems on which we all depend.”
Co-author, Stanford biologist Paul Ehrlich, states that “when humanity exterminates populations and species of other creatures, it is sawing the limb on which it is sitting, destroying working parts of our own life support system”.
To slow the sixth mass extinction, the authors call for immediate global action, such as outlawing the wildlife trade and listing species with populations under 5000 as critically endangered on the International Union for Conservation of Nature’s Red List.
As population extinctions continue, some of the species on the brink will likely become extinct, and some of the under-5 000s will be pushed to the brink.
The research shows that proportionally, more bird species are imperilled, followed by amphibians, then mammals and reptiles.
In regions where disappearing species are concentrated, regional biodiversity collapses are likely occurring.
The human-caused sixth mass extinction is likely to be accelerating for several reasons.
“First, many of the species that have been driven to the brink will likely become extinct soon.
“Second, the distribution of those species highly coincides with hundreds of other endangered species surviving in regions with high human impacts, suggesting ongoing regional biodiversity collapses. Third, close ecological interactions of species on the brink tend to move other species towards annihilation when they disappear – extinction breeds extinctions.”
As humanity’s numbers have grown, this has come to pose an “unprecedented threat” to the vast majority of its living companions, through habitat loss and fragmentation, illegal trade, overexploitation, pollution and toxification “with climate disruption becoming a major cause of species endangerment”.
“Today, species extinctions are hundreds or thousands of times faster than the ‘normal’ or ‘background’ rates prevailing in the last tens of millions of years. Every time a species or population vanishes, Earth’s capability to maintain ecosystem services is eroded to a degree, depending on the species or population concerned.
“Each population is likely to be unique and therefore likely to differ in its capacity to fit into a particular ecosystem and play a role there.
“The effects of extinctions will worsen in the coming decades, as losses of functional units, redundancy, and genetic and cultural variability change entire ecosystems.”
Consider that more than 400 vertebrate species became extinct in the last 100 years – extinctions that would have taken up to 10 000 years in the normal course of evolution.
“The reason so many species are being pushed to extinction by anthropogenic causes is indicated by humans and their domesticated animals being some 30 times the living mass of all the wild mammals that must compete with them for space and resources.
“Although it’s more immediate than climate disruption, its magnitude and likely impacts on human well-being are largely unknown by governments, the private sector and civil society. The conservation of endangered species should be elevated to a national and global emergency for governments and institutions equal to climate disruption.”