Ecosystem Crises Interactions. Merrill Singer. Читать онлайн. Newlib. NEWLIB.NET

Автор: Merrill Singer
Издательство: John Wiley & Sons Limited
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Жанр произведения: Физика
Год издания: 0
isbn: 9781119570011
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schouteni), Swire’s snailfish (Pseudoliparis swirei), and the Tapanuli orangutan (Pongo tapanuliensis) (College of Environmental Science and Forestry 2018). The latter, a native of Batang Toru, Sumatra, is considered the most imperiled great ape in the world. It is estimated that there are only 800 Tapanuli orangutans now living in a fragmented habitat that is spread over about 250 000 acres of forested lands. Insects, like the baffling beetle and a new type of exploding ant (Colobopsis explodens)—so named because a specialized group of its workers can rupture their abdomens to release a toxic liquid to deter invaders (Laciny et al. 2018)—represent more than half of all newly found species.

      The discovery of new species is currently occurring at about twice the overall historic average because of the number of researchers in the field, the availability of funding, and technological advances. Additionally, a number of biodiversity hotspots, where species variety is at its peak, are now known. Stutz (2009) notes that “these are found in Madagascar, India, Indonesia, South America, and Southeast Asia. Along the Mekong River watershed … more than a thousand new species have been discovered over the last 10 years—an average of two new species each week—and the pace of discovery appears to be unabated. Running 3000 miles through China, Myanmar, Laos, Thailand, Cambodia, and Vietnam, the Mekong and its surrounding mountains and forests were always known to hold extraordinary reserves of biodiversity, more species per unit area than any river other than the Amazon.” Additionally, the tropical forests of the Annamite Mountains along the border of Laos and Vietnam have proven to be a lost world that persisted through the last ice age. These poorly trafficked places have been made even more inaccessible by political instability and war.

      When new species are identified and described, they must be named, using what is called a Latin binomial (e.g., Homo sapiens), though it is not always actually in Latin. A thick, 18‐chapter book, the International Code of Zoological Nomenclature (International Commission on Zoological Nomenclature 2012), specifies how new species are named. Rules include: 1) the name must be unique and not in use; 2) the name should not give offence on any grounds; and 3) the discoverer cannot name the species after her‐ or himself. None of the rules bar name‐givers from using humor, however. For example, there are five species of the small round fungus beetle that are named Gelae baen (to sound like “jelly bean”), Gelae balae (“jelly belly”), Gelae donut (“jelly doughnut”), Gelae fish (“jelly fish”), and Gelae rol (“jelly roll”). The right to inject humor explains the naming of a newly discovered Panamanian caecilian that spends most of its life underground: upon winning a contest to raise money for the Rainforest Trust, which allowed the winner to name the new species, Aidan Bell, co‐founder of the British sustainable building materials company EnviroBuild, selected the name Dermophis donaldtrumpi, after the U.S. president. Bell felt that the amphibian’s tendency to keep its head buried in the ground was similar to Donald Trump’s do‐nothing approach to climate change. Unfortunately, Dermophis donaldtrumpi is in line to be added to the vulnerable species list as it is “in danger of becoming extinct as a direct result of its namesake’s climate policies,” Bell said in a statement released to the press (quoted in Guy 2018).

      Ironically, in the midst of the current sixth global extinction of species, when biodiversity is in rapid retreat, science is experiencing a golden age of new species discovery, some examples of which may go extinct not long after they are first identified.

      2.3.2.1 Extinction

      An example of the latter can be seen by looking at Yellowstone National Park as an ecosystem. When the U.S. government designated almost 3500 acres for the park in 1872, there were hundreds of wolves roaming the area, preying especially on large herds of elk and bison. In 1914, fearing the impact of the wolves on those herds, but also on privately owned livestock grazed on public land, Congress appropriated funds to destroy wolves, prairie dogs, and other animals injurious to agriculture and animal husbandry. Park Service hunters carried out these orders, and by 1926 wolves were virtually eliminated from Yellowstone. Loss of this keystone predator started a top‐down trophic cascade. No longer preyed on by the wolves, elk populations exploded and began competing for food resources such as grasses, sedges, and reeds. As a result, these plants did not have time or space to grow. Overgrazing had direct influences on other species, such as fish, beaver, and songbirds, which relied on the plants and their products for survival. Moreover, stream banks began eroding as wetland plants failed to anchor soil and sediments, while lake and river temperatures increased as trees and shrubs failed to provide shaded areas. In the end, it was realized that the complex web of relations that sustained the Yellowstone ecosystem required the presence of wolves, and beginning in the 1990s, in response to a call that began with the biologist Aldo Leopald, the U.S. government began reintroducing them (from Canada). The results have been a shrinking of elk populations, improvements in vegetative cover, and recovery of beaver and songbird populations. According to Doug Smith, a wildlife biologist in charge of the Yellowstone Wolf Project, “[i]t is like kicking a pebble down a mountain slope where conditions were just right that a falling pebble could trigger an avalanche of [positive] change” (quoted in Farquhar 2019).

      Unfortunately, this kind of turnaround is not the norm. A recent statistical analysis of 51 bird species currently recorded on the International Union for Conservation of Nature (IUCN) Red List as critically endangered, for example, concluded that eight should be reclassified as already extinct or very close to extinction (Butchart et al. 2018). Stuart Butchart, the principle investigator on the study, explains that: “Ninety per cent of bird extinctions in recent centuries have been of species on islands … However, our results confirm that there is a growing wave of extinctions sweeping across the continents, driven mainly by habitat degradation and disappearance from unsustainable agriculture and logging” (BirdLife International 2018).

      Aside from the loss of unique lifeforms, extinctions like these are important because when they occur, they alter key processes needed for the sustainability of Earth’s ecosystems (Loreau et al. 2002; Wardle et al. 2011). Biodiversity loss can undercut the viability of ecosystems by diminishing their ability to respond to environmental change and disruption.

      2.3.2.2 The species quandary