The earth sees an unprecedented loss of species, which some ecologists call a sixth massive extinction.
In May a report from the United Nations warned that 1 million species are threatened with extinction. More recently, 571 plant species were declared extinct.
But extinction has occurred as long as life on earth has existed. The important question is, has the rate of extinction increased?
Our research, published today in Current Biology, has shown that some plants are extinct up to 350 times faster than the historical average – with devastating consequences for unique species.
Madagascar is home to around 12,000 plant species, 80% of which are endemic (not found anywhere else). This includes the baobab
Measuring the extinction rate
& # 39; How many species will die out & # 39; is not an easy question to answer. To begin with, there is a lack of accurate data on contemporary extinctions from most parts of the world.
And species are not equally distributed – for example, Madagascar has around 12,000 plant species, 80% of which are endemic (not found anywhere else). In the meantime, only 1,859 species live in England, of which 75 (only 4%) are endemic.
Areas such as Madagascar, which have an exceptionally high biodiversity and are at high risk of human destruction, become & # 39; hotspots & # 39; called.
Purely based on numbers, it is expected that hotspots for biodiversity will die out more than coldspots such as England.
But that does not mean that cold spots are not worth preserving – they usually contain completely unique plants.
We are part of an international team that has recently investigated 291 modern extinctions of plants between hot and cold spots for biodiversity.
We looked at the underlying causes of extinction, when they occurred, and how unique the species was. Armed with this information, we asked how extinctions differ between hot and cold spots for biodiversity.
It is not surprising that we found hotspots that lost more species, faster than coldspots.
Agriculture and urbanization were major causes of the extinction of plants in both hot and cold spots, confirming the general belief that habitat destruction is the main cause of most extinction.
In general, herbaceous perennials such as grasses are particularly vulnerable to extinction.
Cold spots, however, lose more uniqueness than hot spots. For example, seven extinctions with a cold spot led to the disappearance of seven genera, and in one case even to an entire plant family.
It is therefore clear that cold spots also represent important reservoirs of unique biodiversity that must be preserved.
We also show that recent extinction rates were at their peak 350 times higher than historical extinction rates.
Scientists have previously speculated that modern plant extinctions will surpass background rates by thousands of times over the next 80 years.
So why are our plant extinction estimates so low?
First, a lack of comprehensive data limits the conclusions that can be drawn about modern extinctions.
Second, plants are unique – some live extremely long and many can remain in low densities through unique adaptations, such as being able to reproduce in the absence of partners.
Let us look at a hypothetical situation in which we have only five living individuals of the baobab of Grandidier (Adansonia grandidieri) in the wild. These iconic Madagascar trees are one of only nine living species of their kind and can live for hundreds of years.
Therefore, some individual trees can hang there & # 39; & # 39; (a situation commonly called & # 39; extinction debt & # 39;), but will inevitably die out in the future.
Finally, it is a challenge to declare a plant extinct simply because they are often very difficult to recognize and we cannot be sure that we have found the last living individuals.
Indeed, a recent report rediscovered 431 plant species that were previously thought to be extinct.
Thus, real plant extinction rates and future extinctions are likely to far exceed current estimates.
There is no doubt that loss of biodiversity, together with climate change, are some of the greatest challenges facing humanity.
The impact of climate change, together with man-made habitat destruction, is expected to be particularly serious for plant biodiversity.
The current estimates of the extinction of plants are undoubtedly gross underestimations.
However, the characters are crystal clear. If we were to summarize Earth's 4.5 billion-year-old history in one calendar year, life evolved somewhere in June, dinosaurs appeared somewhere around Christmas, and the Anthropocene begins in the last millisecond of New Year's Eve.
The modern extinction rates that are hundreds of times higher than the historical figures during such a short period will be disastrous for the future of our planet.
WHAT SPEAKS FOR THE LOT OF PLANET PLANTS AND ANIMALS?
Nature now has more problems than ever before in human history, with extinction looming over a million species of plants and animals, experts say.
That is the most important finding of the first comprehensive United Nations report on biodiversity – the diversity of plant and animal life in the world or in a particular habitat.
The report – published on May 6, 2019 – says that species are lost dozens or hundreds of times faster than in the past.
Many of the worst effects can be prevented by changing the way we grow food, produce energy, deal with climate change and throw away waste, the report said.
The 39-page summary of the report highlighted five ways in which people reduce biodiversity:
– Forests, grasslands and other areas turn into farms, cities and other developments. The loss of habitat makes plants and animals homeless. Approximately three-quarters of the Earth's land, two-thirds of the oceans and 85% of the crucial wetlands have been severely changed or lost, making it harder for species to survive, the report said.
– Overfishing of the world's oceans. A third of the world's fish stocks are overfished.
– Allowing climate change by burning fossil fuels to make it too hot, wet or dry for some species to survive. Almost half of the land mammals in the world – excluding bats – and nearly a quarter of the birds have already hit their habitats hard by global warming.
– Polluting land and water. Every year, 300 to 400 million tonnes of heavy metals, solvents and toxic sludge are dumped into the world's waters.
– Allowing invasive species to displace native plants and animals. The number of invasive alien species per country has risen by 70 percent since 1970, with one species of bacteria threatening nearly 400 species of amphibians.
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