A Third of Cacti Facing Extinction Due to Human Encroachment
October 6, 2015
Agence France-Presse & Renee Lewis / Al Jazeera America
Cacti are among most the threatened taxonomic groups on Earth, ahead of mammals and birds, says new global study by the International Union for Conservation of Nature. As a report in the journal "Science" warned in 2014, the global extinction rate is now 1,000 times faster than before humans began altering their habitats.
A Third of Cacti Facing Extinction
Due to Human Encroachment, Study Finds
Agence France-Presse & Al Jazeera America
(October 5, 2015) -- Thirty-one percent of cacti, some 500 species, face extinction due to human encroachment, according to the first global assessment of the prickly plants, published Monday.
The finding places the cactus among the most threatened taxonomic groups on Earth, ahead of mammals and birds and just behind corals, according to the inter-government group International Union for Conservation of Nature (IUCN).
"The results of this assessment come as a shock to us," lead researcher Barbara Goettsch, co-chair of the IUCN's Cactus and Succulent Plant Specialist Group, said in a statement. "We did not expect cacti to be so highly threatened."
The IUCN Red List is widely recognized as the gold standard for measuring extinction risk for animals and plants.
Cacti -- native to the Americas, but introduced over centuries to Africa, Australia and Europe -- are crucial links in the food chains of many animals, including humans. They are an essential sources of sustenance and water for deer, woodrats, rabbits, coyotes, lizards and tortoises which, in return, help spread cacti seeds.
Cactus flowers supply nectar to hummingbirds and bats, along with bees, moths and other insects that help pollinate the largely desert-dwelling plants. In many parts of Central and South America, cacti are used by people for food and medicine.
Mexico's prickly pear cactus stem, for example, is highly nutritious, while the root of another species listed as near threatened -- Ariocarpus kotschoubeyanus -- is commonly used as an anti-inflammatory.
Depending on the species and the region, different forces have driven the decline in cacti, found the study, published in Nature Plants.
The top threat to cacti is expanding agriculture, especially in northern Mexico and the southern part of South America.
Species native to coastal areas are being decimated by residential and commercial development, while in southern Brazil conversion of land for eucalyptus plantations is harming at least 27 species, some of them already on the endangered list.
"Their loss could have far-reaching consequences for the biodiversity and ecology of arid lands and for local communities dependent on wild-harvested fruits and stems," Goettsch said.
Researchers were also surprised to find that illegal trade in highly prized plants is also a key factor in their disappearance. "The scale of the illegal wildlife trade -- including trade in plants -- is much greater than we previously thought," said Inger Andersen, IUCN director general.
Some 86 percent of threatened cacti used in horticulture are taken from wild populations rather than cultivated, other studies have shown. Europe and Asia are the biggest markets for this illicit trade.
Mining is also a problem, as illustrated by the critically endangered -- the highest level of threat before extinction -- Arrojadoa marylaniae, which only grows on a single type of white quartz rock.
Even the expansion of fish farming in huge man-made basins has encroached on cacti habitat as land is cleared for aquaculture, especially in northwestern Mexico.
Cacti range in size from one half-an-inch in diameter, to some 62 feet high. The iconic Saguaro cactus -- de rigeur in Hollywood Westerns -- grows nearly as tall, and lives for up to 200 years.
Earth Heading toward Another Mass Extinction
Renee Lewis / Al Jazeera America
(May 30, 2014) -- Species are now disappearing at a rate of up to 1,000 times faster than they did before humans started walking the earth, a new study says.
"The Biodiversity of Species and their Rates of Extinction, Distribution, and Protection" was published Thursday in the journal Science, and it warned that the world is on the brink of its sixth great extinction.
Mass extinctions have wiped out the majority of life on Earth at least five times. About 66 million years ago, a mass extinction killed off the dinosaurs and three out of four species on Earth, the report said.
Though such extinctions are often associated with asteroids, the worst mass die-off around 252 million years ago, which wiped out 90 percent of life on Earth, was caused by methane spewing microbes, according to a new theory.
The microbes produced much the same effect as climate change -- a sudden rise in temperatures and acidification of the oceans. Both phenomena can be observed today due to global warming, and man-made climate change was cited by the report as one factor making traditional habitats unlivable for many species.
Though scientists have been aware that mass extinctions are occurring, this study calculates the actual rate of extinction -- not just the number of species disappearing -- before and after humans appeared on the scene.
In 1995, Duke University's Stuart Pimm of Duke University, the study's lead author, calculated that before humans were on the scene, one out of 1 million species went extinct every year.
Today, the rate is between 100 to 1,000, according to Pimm, who also heads a conservation nonprofit called Saving Species.
That trend can be reversed if biologists can pinpoint where vulnerable species are, according to the study. Once they have that information, they can try to save the species by preserving their habitats.
Habitat loss is the number one factor in the accelerating rates of global extinction, the study said. Humans have developed and taken over too much land, and many species no longer have a place to live.
Pimm and co-author Clinton Jenkins of the Institute of Ecological Research in Brazil suggested that the increasing availability of smartphones and conservation apps could allow the public to help researchers find endangered animals
This online crowdsourcing of species distribution could expand online databases and could help scientists better identify and protect vulnerable species. That data can then be combined with information already available on changing land and ocean use to better identify and protect vulnerable species.
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