www.READMETRO.com august 2017
FOCUS /
00
The sixth mass extinction is under way
Q&A
Gerardo Ceballos
Ecology professor at the Universidad Nacional Autónoma de México, and co-author of sixth mass extinction study
Are we close to the sixth mass extinction? We are not close to the sixth mass extinction, we are already living it! In 2015, we published an article confirming that the number of species that at normal rates had to extinguish in 10 thousand years, already disappeared during the past 100. This is a very rapid rate of extinction. Human impact indicates that we will face even greater extinction rates in the coming years.
|ISTOCK
5
previous mass extinctions PHOTOS: CREATIVE COMMONS
Ordovician-Silurian (440 million years ago)
Late Devonian extinction (364 million years ago)
Around 86 per cent of life on Earth was wiped out. At that time most life was in the sea. Scientists believe that two events led to crisis: glaciation and falling sea levels.
Nearly 75 per cent of Earth’s species were lost in this event that lasted 20 million years. There is evidence of a series of extinction pulses within this period. It is believed that it was caused by large glaciations.
Permian–Triassic (251 million years ago) This event is called the “Great Dying” and is considered the worst mass extinction of all times, because around 96 per cent of species disappeared. It was caused by an enormous volcanic eruption. All life on Earth today was descended from the 4 per cent of species that survived.
So, it’s our fault? Of course, man is the cause of this massive extinction and the human activities that contribute to it. They include destruction of natural environments, illegal trafficking of species, overexploitation, pollution, environmental toxicity, invasion of exotic species and climate change. All these factors together are causing populations and species to be extinguishing at a very high rate.
SOURCE: PNAS
LOW CONCERN ENDANGERED
100 90 80 70 60 50 40 30 20 10 0
AMPHIBIANS
200
The percentage of decreasing species
REPTILES
Several studies have indicated that our planet is about to experience the sixth mass extinction of species due to human actions, including devastation of habitats, pollution, over exploitation of natural resources and global warming. Experts told Metro that it is already happening and could lead to fatal consequences. A research recently published by the Proceedings of the National Academy of Sciences of the United States of America (PNAS) called ‘Biological annihilation via the ongoing sixth mass extinction signaled by vertebrate population losses and declines’ revealed that 32 per cent of the 27.6k landbased mammal, bird, amphibian and reptile species studied (comprising nearly half of known vertebrate species) are decreasing in population size and range.
GRAPHIC
BIRDS
Metro World News
“No doubt. The main factors of extinction are the destruction of natural spaces by human expansion, and overexploitation”
MAMMALS
Daniel Casillas
Within the 177 mammal species studied, research found that all of them lost 30 per cent or more of geographic ranges and more than 40 per cent of species have experienced severe population declines. The study adds that this decline in animal Rodolfo Dirzo, professor of biology populations has led several at the Stanford University species of mammals – that were relatively safe one or two decades ago – to be endangered. For example, populations of African lion dropped by 43 years, a very alarming figure. Matzke, researcher at the per cent since 1993 and po- That is why Ceballos says that Australian National University pulations of giraffes dropped we should not wait for 75 per and author of a study about from around 115k in 1985, to cent of Earth’s species to di- the sixth mass extinction, exsappear to to declare that we plained. around 97k in 2016. It is also expected that huOther studies and experts are already facing the crisis. Although there are some mans will be affected most by also consider that the sixth mass extinction imposes dan- disputes whether the Earth’s the extraordinary disappeager to our future (‘mass extinc- sixth mass extinction event al- rance of species due to the altion’ is typically defined as 75 ready has begun or it is about teration of ecosystems. “The most direct implicaper cent decrease of all species to, specialists point out that going to extinct. – Ed.). Gerar- humans are the main cause tion [of mass extinction] that do Ceballos, ecology professor of it. And our activities are the we have begun to document at the National Autonomous main factor that is causing the is that the functioning of University of Mexico and co- disappearance of entire popu- ecosystems, and the resulting lations of animals around environmental services, will author of the investigabe altered, or in some cases the planet. tion, warns that this “The current eliminated. But perhaps more phenomenon is alextinction crisis critical, this extinction involready underway is almost enti- ves the loss of the various maand could mean rely due to hu- nifestations of the evolution the end of civiman impacts, of life on the planet, and relization as we know it. species extinct in the last 100 ranging from present sources of education, direct (humans inspiration, joy and natural “We are not years killing certain culture for humans,” Rodolclose to the species for mo- fo Dirzo, professor of biology sixth mass exney, e.g. killing at Stanford University, U.S. tinction, we are of rhinos for fake, added. already in the sixth However, there is a way to fraudulent medical mass extinction!” Ceballos told to Metro. “We are treatments in China and el- stop the sixth mass extinction. endangering the viability of sewhere) to indirect (habitat In order to achieve that, accorloss due to rainforest destruc- ding to experts, it is necessary civilization as we know it.” According to statistics, two tion) to global (global war- to reduce the rapidly growing hundred species extinct in 100 ming, pollution, etc.),” Nick rates of the human population
LAND VERTEBRATES
Unlike the five previous mass extinctions when volcanic activity, asteroid impacts and glaciations ended with a lot of Earth’s species, now the decisive factor are humans. Metro investigates how is it possible to survive.
to end the overexploitation of natural resources, end illegal trafficking of animals and combat global warming. But these solutions are necessary in the short term. “At present extinction rates, studies indicate that humans have less than 20 years to avoid the complete extinction of the species of the planet,” Ceballos concluded.
Triassic–Jurassic (199 million to 214 million years ago) Around 70 to 75 per cent of all species were eliminated during two or three phases of this extinction. An asteroid impact, climate change, and flood basalt eruptions have all been blamed for causing the crisis.
What does this extinction imply? We are endangering the wellbeing of humans and, in the long term, the viability of civilization as we know it. Because the capacity of Earth to support life depends on the plants and wild animals. No other planet has an atmosphere like that and the amount of gases that maintain this atmosphere depends on the plants and animals, in addition to many other factors. How to avoid it? We must understand and counteract the human activities that are causing the mass extinction. There are three of them: rapid growth of human population, excessive consumption and inefficient technologies. It is also very important that human population becomes an actor, and stop being a spectator.
Cretaceous-Tertiary (65 million years ago) This mass extinction is the most well-known, because it caused disappearance of dinosaurs. According to statistics, 75 per cent of all species became extinct as a result of a combination of volcanic activity, asteroid impact, and climate change.