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According to a recent analysis, the sixth mass extinction of wildlife on Earth is accelerating. More than 500 species of land animals are on the brink of extinction and are likely to be lost within 20 years; the same number were lost over the whole of the last century. The scientists say that without the human destruction of nature, this rate of loss would have taken thousands of years and they warn that this may be a tipping point for the collapse of civilisation. 

The analysis, published in the journal Proceedings of the National Academy of Sciences, looked at data on 29,000 land vertebrate species compiled by the International Union for Conservation of Nature (IUCN) Red List of Threatened Species and BirdLife International. The scientists identified 515 species with populations below 1,000 and about half of these had fewer than 250 individuals remaining. 

What is a Mass Extinction Event?

A mass extinction is usually defined as a loss of about three quarters of all species in existence across the entire Earth over a “short” geological period of time. Given the vast amount of time since life first evolved on the planet, “short” is defined as anything less than 2.8 million years.

The Analysis

The land vertebrates on the brink of extinction, with fewer than 1,000 individuals left, include the Sumatran rhino, the Española giant tortoise and the harlequin frog. Historic data for 77 of these species shows that they had lost 94% of their populations in the last century. Further, more than 400 vertebrate species became extinct in the last century, extinctions that would have taken up to 10,000 years in the normal course of evolution, illustrating humanity’s profound effect on the planet and those that live on it. 

The analysis also showed that 388 species of land vertebrates had populations under 5,000 individuals and 84% lived in the same regions as the species with populations under 1,000, creating the conditions for a domino effect. The scientists warned that ‘extinction breeds extinction’, where close ecological interactions of species on the brink tend to move other species towards extinction, creating the domino effect. 

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sixth mass extinction
A graph showing the number of species with fewer than 1,000 individuals and number of species whose conservation status had been evaluated by the IUCN. These are the species most likely to be lost in the sixth mass extinction event (Source: PNAS).

Causes

The scientists say that the ongoing sixth mass extinction may be the most serious environmental threat to the persistence of civilisation, because it is irreversible. They say that it is caused by an ever-increasing population and consumption rates. Further, species are links in ecosystems and, as they disappear, the species they interact with are likely to disappear as well.

When a species dies out, the Earth’s ability to maintain ecosystem services is eroded to a degree. Humanity needs a relatively stable climate, flows of fresh water, agricultural pest and disease-vector control and pollination for crops, all services that will be impacted as the sixth mass extinction accelerates. 

Professor Paul Ehrlich of Stanford University and one of the researchers of the analysis, says, “When humanity exterminates other creatures, it is sawing off the limb on which it is sitting, destroying working parts of our own life-support system. The conservation of endangered species should be elevated to a global emergency for governments and institutions, equal to the climate disruption to which it is linked.”

Consequences of the Sixth Mass Extinction

When the number of individuals in a population or species drops too low, its contributions to ecosystem functions and services become unimportant, its genetic variability and resilience is reduced and its contribution to human welfare may be lost. An example of this includes the overhunting of sea otters, the main predator of kelp-eating sea urchins. A population boom of urchins wreaked havoc on kelp forests in the Bering Sea, leading to the extinction of the kelp-eating Steller’s sea cow.

Another is the bison, which was a keystone species in North America. At one time, it was maintaining the entire ecosystem, supplying meat, robes and fertilisers to Native Americans, and later to Europeans. Is it estimated that 200 years ago, there were 30 to 60 million individuals, but overharvesting for meat and skins and land conversion for farming decimated most populations. By 1844, there were 325 individuals left. They have since recovered to 4,000 wild bison and 500,000 living in enclosures, but the species has not reclaimed its ecological role and its habitats- the prairies- have been mostly destroyed. 

Many endangered species are being affected by the wildlife trade, both legal and illegal, which poses a threat to human health, is a major cause of species extinction and is eroding the ecosystem services that are vital for our survival. The scientists note that the ban on wildlife trade imposed by the Chinese government could be a major conservation measure for many species on the verge of extinction if imposed properly. They propose including wild species for consumption as food as well as medicinal use and pets to curb the acceleration of the sixth mass extinction.

Previous Mass Extinction Events

There have been five mass extinction events during the last 450 million years, each destroying 70-95% of the species of plants, animals and microorganisms that existed previously. These events were caused by massive volcanic eruptions, depletion of ocean oxygen or collision with an asteroid. In each event, it took millions of years to regain the numbers of species comparable to those before the extinction event.

As such, an estimated 2% of the species that ever lived are alive today. Species extinction rates are today hundreds of thousands of times faster than the ‘normal’ rates occurring in the last tens of millions of years. The losses that we are seeing have mostly occurred since our ancestors developed agriculture 11 000 years ago. 

Can We Stop the Sixth Mass Extinction?

The scientists also propose classifying all species with less than 5 000 individuals as critically endangered on the IUCN list as well as implementing a global comprehensive binding agreement requiring parties to address the extinction crisis, especially through tackling the illegal and legal wildlife trade. 

Mark Wright, the director of science at WWF, says, “The numbers in this research are shocking. However, there is still hope. If we stop the land-grabbing and devastating deforestation in countries such as Brazil, we can start to bend the curve in biodiversity loss and climate change. But we need global ambition to do that.”

Humanity relies on biodiversity for its health and wellbeing. The recent COVID-19 pandemic is an example of the dangers of interfering with and damaging the natural world. The scientists urge that a booming human population, destruction of habitats, wildlife trade, pollution and the climate crises must all be urgently tackled. 

There is time to save species, but the window of opportunity is almost closed. We must save what we can, or lose the opportunity to do so forever. There will likely be more pandemics in the future if we continue destroying habitats and trading wildlife for consumption. The fate of humanity and most living species is at stake; it is therefore imperative that we act now. 

A new study has indicated that 31.7% of tropical African flora species are at risk of going extinct, affecting those countries that rely on its biodiversity for tourism and fuel.

In the study, tropical flora was assessed across the continent. The findings were published in the Science Advances Journal and used an assessment process outlined by the International Union for Conservation of Nature (IUCN) Red List criteria.

The research demonstrated that 6,990 of the 22,036 species studied, or 31.7%, are at risk of extinction. Much of western African countries, Ethiopia, and parts of Tanzania and the Democratic Republic of Congo are the hardest-hit regions, standing to lose more than 40% of their flora. The species both at risk and potential risk include trees, shrubs, herbs and woody vines.

Biodiversity Loss in Africa

Loss of biodiversity will be particularly problematic in tropical Africa, “a region of incredible diversity but with major social and political challenges and expected rapid population growth over the next decades,” said lead researcher Dr Thomas Couvreur, a botanist at The French National Institute for Sustainable Development.

The situation could get worse. As well as the species that are at risk of extinction, a further 33.2% of the species studied are rare and could potentially be threatened with extinction. Major threats to biodiversity, especially in areas of exceptional plant diversity, primarily in the tropics, are often linked to industrial-scale activities such as timber exploitation or large plantations, mining and agriculture.

Research projects such as these are vital; while almost 90% of mammals and two-thirds of birds have been assessed, less than 8% of plants have been assessed, a surprising find considering how crucial plants are to the Earth’s ecosystems. This lack of data is especially true for tropical regions, such as the ones found in Africa, where the flora is extremely diverse, but have been poorly documented. 

Biodiversity going extinct has a knock-on effect. For example, some of the plant species that the African forest elephant eat can only germinate by passing through the animal’s digestive tract. Without these tree species, the elephants cannot eat and without the elephants, the tree species cannot reproduce, further emphasising the need to preserve these ecosystems.

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Commiphora is listed as endangered in four regions of Africa, including Ethiopia. (Source: Vinayaraj)

This assessment process aims to provide information on the conservation status of large numbers of species, following the guidelines of Preliminary Automated Conservation Assessments (PACA). By using PACA, the entire flora of a given area can be assessed. This allows species, both at threat and requiring additional attention, to be identified. 

The new approaches used in the study also provide useful guidelines for others to follow; they reduce cost, time and increase the potential of carrying out large-scale assessments. This is important as information can be gleaned quicker and at a cheaper rate. 

Professor Bonaventure Sonké, Professor at the Laboratory of Systematic Botany and Ecology of the Ecole Normale Supérieure (University Yaounde 1, Cameroon), says that the results were possible ‘because the partners involved agreed to share their data’. He adds that this creates ‘a strong signal to encourage researchers to share their data’.

The importance of sharing data is being realised and there is hope that this collaborative approach will produce solutions quicker. However, it may not be quick enough. The UN Environment Programme says, “No continent will be struck as severely by the impacts of climate change as Africa. Given its geographical position, the continent will be particularly vulnerable due to its considerably limited adaptive capacity, which will be exacerbated by widespread poverty.”

Despite this, perhaps the immensity of the challenges facing the continent can be mitigated through new approaches such as the ones used in the study. Dr Covreur says that “this study is the first large-scale assessment of the potential conservation status of the tropical African flora, explicitly using the IUCN’s methodology. While the results of the study are concerning, it is important that more studies such as these are conducted, so that threats facing biodiversity can be ascertained and managed.”

Article 14 of the UN Convention on Biological Diversity explicitly states that environmental impact assessments (EIAs) should be conducted before implementing projects that could impact on biodiversity in an area. To reduce risks linked to environmental concerns, EIAs should identify adverse impacts by projects on biodiversity and indicate measures to avoid, minimise and offset these impacts. This process must be followed to ensure that the richness of these countries’ biodiversity is preserved. 

North America has lost 29% of its bird populations- 2.9 billion birds- in the last 48 years. It’s not just the endangered species, even the common birds like sparrows, warblers, and finches have also vanished from the sky, a new study published in the journal Science reveals. Scientists fear that the decline signals a major crisis since birds play critical roles in distributing seeds, disposing of rotting carcasses, and even pollinating plants. 

Bird Population Decline in North America

A team of researchers from the US and Canada analysed almost five decades of population data of 529 bird species collected from multiple long-term bird-monitoring data sets. They found that over 90% of the total decline recorded was among 12 bird families, including sparrows, warblers, blackbirds, and finches. Grassland birds suffered the most with a 53% reduction recorded in their population since 1970. With over 700 million fewer individuals existing today, nearly 75% of all examined grassland bird species are steadily declining. Shorebirds living in sensitive coastal habitats have lost more than one-third of their population. 

Scientists fear that many bird species could soon suffer the fate of the passenger pigeon (Ectopistes Migratorius) —  a bird that once numbered in billions, but silently went extinct in the early 1900s.

“Multiple, independent lines of evidence show a massive reduction in the abundance of birds in North America,” says Ken Rosenberg, the study’s lead author and a senior scientist at the Cornell Lab of Ornithology and American Bird Conservancy. “We expected to see continuing declines of threatened species. But for the first time, the results also showed pervasive losses among common birds across all habitats, including backyard birds.”

Analysing the data recorded by a network of 143 weather radars across North America, scientists also tracked the changes in nighttime spring migration of birds from 2007 and 2017. The radars, which can detect avian migration even in areas where birds are otherwise poorly monitored on the ground, revealed a 14% decline in migratory birds since 2007.

Where did the birds go?

“It’s a wake-up call that we’ve lost more than a quarter of our birds in the US and Canada,” says co-author Adam Smith from Environment and Climate Change Canada. “But the crisis reaches far beyond our individual borders. Many of the birds that breed in Canadian backyards migrate through or spend the winter in the US and places farther south — from Mexico and the Caribbean to Central and South America. What our birds need now is a historic, hemispheric effort that unites people and organisations with one common goal: bringing our birds back.”

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The passenger pigeon

While the researchers did not closely examine what caused the decline, they say the phenomenon in North America is similar to those observed elsewhere in the world, and the causes are likely to be similar.

For example, widespread conversion of grasslands to farmlands and urban areas, and the extensive use of toxic pesticides had earlier caused the decline of grassland bird population across Europe. North American grassland birds today face great threat from such human activities as their breeding and wintering grounds have been turned into agricultural lands and urban centers.  

Previous studies have discovered increasing bird mortality in the US due to hunting by predators including feral cats; collisions with glass, buildings, and other structures; pervasive use of pesticides, and widespread declines in insects — an essential food source for birds. Climate change is compounding these challenges by altering habitats and reducing the number of plant species that birds depend on for their survival. 

Though the study portrays a grim picture, all hopes are not lost. “The story is not over,” says co-author of the paper Michael Parr, president of American Bird Conservancy. “There are so many ways to help save birds. Some require policy decisions such as strengthening the Migratory Bird Treaty Act. We can also work to ban harmful pesticides and properly fund effective bird conservation programs. Each of us can make a difference with everyday actions that together can save the lives of millions of birds — actions like making windows safer for birds, keeping cats indoors, and protecting habitat.”

The study lists out a few promising examples of bird population rebounds. Waterfowl- ducks, geese, and swans- have made a remarkable recovery over the past 50 years in the US after the government allocated funds for wetland protection and restoration. Raptors such as the Bald Eagle have also made a remarkable recovery since the 1970s following a countrywide ban on the pesticide DDT and the introduction of endangered species legislation in the US and Canada. 

The first ever global analysis of plant extinction found that over 570 species of plants have gone extinct in the last 250 years. Researchers believe even these numbers underestimate the true levels of the ongoing extinction.

571 plant species have completely disappeared from Earth in the last 250 years- more than twice the number of bird, mammal and amphibian species to have gone extinct in the same period combined.

The extinction rate is 500 times greater now than before the industrial revolution. The study was conducted by a team of researchers at the Royal Botanic Gardens, Kew, and Stockholm University.

The pattern of extinction of plants is strikingly similar to that of animals, though it doesn’t seem to be based on evolutionary patterns, as it is with the latter.

The majority of plant extinctions occurred in biodiversity ‘hotspots’ in the Tropics and the Mediterranean, including places like Australia, India, and Hawaii. Of all the extinct plant species numbered throughout the world, half were once found on islands and 18 percent once flourished in the Pacific.

“This probably reflects the high proportion of unique species (endemics) in island biotas and their vulnerability to biological invasion,” the authors suggest. “Consistent with this, we found that extinct species have narrower ranges than seed plants as a whole. We also found that most extinct plants were woody perennials and from the wet tropics or subtropics.”

Why do plants go extinct?

Many new plant species might also be headed for extinction because of habitat loss, climate change, and human exploitation. Around a third of the 90,000 species the team analysed could be considered threatened in some way.

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The Saint Helena olive, Nesiota elliptica, first discovered in 1805. It went extinct in 2003.
Photograph: Kew Gardens

To reach these conclusions, the researchers scoured every journal and plant database at their disposal, beginning with a 1753 compendium by pioneering botanist Carl Linnaeus and ending with the regularly updated IUCN Red List of Threatened Species, which maintains a comprehensive list of endangered and extinct plants and animals around the world. After combining and cross-checking the various extinction reports, the team compared the results to the natural or “background” extinction rates for plants, which a 2014 study calculated to be between 0.05 and 0.35 extinctions per million species per year.

Despite the gloomy outlook for planet Earth, the study does provide a glimmer of hope. The team found that 430 plant species which were thought to have gone extinct were rediscovered in the period they investigated. However, it should be noted that 90 percent of these rediscovered plants have a high extinction risk.

Researchers called for a number of measures to stop plant extinction: recording all the plants across the world, supporting herbaria, which preserve plant specimens for posterity, supporting botanists who carry out vital research, and teaching our children to see and recognise local plants. “We urge botanists to compile data on search effort, species density, abundance and detectability and to engage local people in the search for their missing biodiversity.” the authors say. “Such efforts will improve our understanding of genuine extinctions and help target future conservation action.”

Featured image: An artist’s rendering of extinct plant Sigillaria

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