Threatened arthropods

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Threatened arthropods are defined here as any of a number of species within the phylum Arthropoda, whose extinction is likely in the foreseeable future. Estimating the number of threatened arthropod species is extremely difficult, primarily because a vast number of the species themselves are not yet named or described. Furthermore, according to Deyrup and Eisner, [1] "The rate of destruction and degradation of natural habitats is currently so great that there are not nearly enough biologists to even catalog the arthropod species that are suddenly on the edge of extinction." In any case, independent estimates indicate that there are millions of undocumented arthropods on Earth. [2]

Contents

Arthropods as a group have been very successful organisms on this planet, comprising over half of all the higher life forms. However the expansion of human activities has led to demise of many arthropod species through the mechanisms of deforestation, conventional farming, slash-and-burn methods in the tropics, habitat fragmentation via urban development, excessive use of pesticides and even the success of forest fire suppression.

The social/political practice whereby a species is given a formal designation as "Endangered" or "Protected" is a different matter, called "Conservation status", and discussed elsewhere; see Endangered Species List for the United States, and IUCN Red List for international purposes. Only a tiny fraction of the planet's endangered arthropods are formally recognized as such, as no one has ever evaluated the conservation status of the vast majority of arthropod species.

Difficulty of estimating numbers of species

The endangered Delhi Sands flower-loving fly. Rhaphiomidas terminatus abdominalis.jpg
The endangered Delhi Sands flower-loving fly.

It is difficult to estimate the total number of endangered arthropod species, since many of the taxa themselves have not been recorded. For example, in North America the estimated number of insect species exceeds 163,000, of which only about two thirds are taxonomically known. [3] An even greater discovery awaiting, over 72 percent of North American arachnids are yet to be named and described. [3]

The total number of living arthropod species is probably in the tens of millions. [2] One conservative estimate puts the number of arthropod species in tropical forests alone at six to nine million species. [4] As a consequence of all of the above, most published estimates of the total number of endangered insects and arachnids are probably low by at least an order of magnitude. [3] Conservatively at least eighty percent of all living animal species are arthropods. [5]

Ecological risks

Since arthropods constitute the majority of the faunal biomass on Earth, their role is vital to the survival of large numbers of insectivores and other animals that prey upon arthropods. This includes enormous numbers of mammals, avafauna, fishes, reptiles and amphibians; in addition, arthropods constitute the bulk of faunal pollinators, so that the survival of crops as well as millions of natural flora species depend on robust and biologically diverse arthropod populations. [6]

The survival of diverse arthropods is essential to propagation of higher animals on the food chain, e.g. those species who prey upon the insectivores and other taxa that consume arthropods. Even if constant arthropod total biomass results after certain arthropod extinctions, the ecosystem stability is compromised by reduction in species numbers. Thus extinction of arthropods species threaten to make extinct hundreds of thousands, if not millions, of higher order birds, amphibians, reptiles and mammals.[ citation needed ]

Mechanisms of arthropod endangerment

Aerial photo of the Anjajavy Forest, Madagascar which holds a number of endangered arthropods. Anjajavyforestrazorback.jpg
Aerial photo of the Anjajavy Forest, Madagascar which holds a number of endangered arthropods.

Most endangerment of arthropod populations is from habitat destruction by growing human populations and related human activities such as agriculture, construction and transportation. [ citation needed ]

Agriculture, in particular has a number of direct effects: a monocultures from intensive practices cannot support the biodiversity nurtured by the predecessor natural environment. [ citation needed ] Normally arthropods represent the largest number of species that are displaced by such farming. In tropical regions the major threat is slash-and-burn agricultural techniques pursued by indigenous peoples in their sometimes only available method of subsistence. [ citation needed ] Pesticide use is also a major threat to arthropod species survival. Pesticides may have an intended effect of killing specified insects in a farming environment; however, considerable pesticide applications kill unintended species by the lack of specificity of most chemical formulations; moreover, much of the insect mortality arises from pesticide runoff entering surface waters or from transporting toxic chemicals to downgradient environments.[ citation needed ]

Habitat fragmentation has special methods of endangerment beyond the amount of land consumed by the fragmenting agent. As an example, consider the construction of a highway, whose width is an effective barrier to arthropod migration. Many arthropods never migrate more than about 200 feet from their place of birth, so a freeway or dual carriageway effectively fragments many arthropod colonies such that they cannot interact. Studies have shown the greater vulnerability to extinction where habitats are fragmented. [7]

Example endangered arthropods

The following is a very small fraction of the potentially hundreds of thousands of endangered arthropods, limited to species which have been formally recognized as to their special conservation status:

The endangered European freshwater crayfish. Ecrevisse a pattes blanches.jpg
The endangered European freshwater crayfish.

See also

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Habitat fragmentation Discontinuities in an organisms environment causing population fragmentation and ecosystem decay

Habitat fragmentation describes the emergence of discontinuities (fragmentation) in an organism's preferred environment (habitat), causing population fragmentation and ecosystem decay. Causes of habitat fragmentation include geological processes that slowly alter the layout of the physical environment, and human activity such as land conversion, which can alter the environment much faster and causes the extinction of many species. More specifically, habitat fragmentation is a process by which large and contiguous habitats get divided into smaller, isolated patches of habitats.

Wildlife conservation Practice of protecting wild plant and animal species and their habitats

Wildlife conservation refers to the practice of protecting wild species and their habitats in order to maintain healthy wildlife species or populations and to restore, protect or enhance natural ecosystems. Major threats to wildlife include habitat destruction/degradation/fragmentation, overexploitation, poaching, pollution and climate change. The IUCN estimates that 27,000 species of the ones assessed are at risk for extinction. Expanding to all existing species, a 2019 UN report on biodiversity put this estimate even higher at a million species. It's also being acknowledged that an increasing number of ecosystems on Earth containing endangered species are disappearing. To address these issues, there have been both national and international governmental efforts to preserve Earth's wildlife. Prominent conservation agreements include the 1973 Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES) and the 1992 Convention on Biological Diversity (CBD). There are also numerous nongovernmental organizations (NGO's) dedicated to conservation such as the Nature Conservancy, World Wildlife Fund, and Conservation International.

Near-threatened species IUCN conservation category

A near-threatened species is a species which has been categorized as "Near Threatened" (NT) by the International Union for Conservation of Nature as that may be considered threatened with extinction in the near future, although it does not currently qualify for the threatened status.

Critically Endangered IUCN conservation category

An IUCN Red List Critically Endangered (CR) species is one that has been categorized by the International Union for Conservation of Nature as facing an extremely high risk of extinction in the wild. As of 2021, there are 6,811 species that are considered to be Critically Endangered. This is out of the 120,372 species currently tracked by the IUCN.

Insect biodiversity

Insect biodiversity accounts for a large proportion of all biodiversity on the planet—over half of the estimated 1.5 million organism species described are classified as insects.

Bird conservation

Bird conservation is a field in the science of conservation biology related to threatened birds. Humans have had a profound effect on many bird species. Over one hundred species have gone extinct in historical times, although the most dramatic human-caused extinctions occurred in the Pacific Ocean as humans colonised the islands of Melanesia, Polynesia and Micronesia, during which an estimated 750–1800 species of bird became extinct. According to Worldwatch Institute, many bird populations are currently declining worldwide, with 1,200 species facing extinction in the next century. The biggest cited reason surrounds habitat loss. Other threats include overhunting, accidental mortality due to structural collisions, long-line fishing bycatch, pollution, competition and predation by pet cats, oil spills and pesticide use and climate change. Governments, along with numerous conservation charities, work to protect birds in various ways, including legislation, preserving and restoring bird habitat, and establishing captive populations for reintroductions.

Endangered species Species of organisms facing a very high risk of extinction

An endangered species is a species that is very likely to become extinct in the near future, either worldwide or in a particular political jurisdiction. Endangered species may be at risk due to factors such as habitat loss, poaching and invasive species. The International Union for Conservation of Nature (IUCN) Red List lists the global conservation status of many species, and various other agencies assess the status of species within particular areas. Many nations have laws that protect conservation-reliant species which, for example, forbid hunting, restrict land development, or create protected areas. Some endangered species are the target of extensive conservation efforts such as captive breeding and habitat restoration.

Defaunation is the global, local or functional extinction of animal populations or species from ecological communities. The growth of the human population, combined with advances in harvesting technologies, has led to more intense and efficient exploitation of the environment. This has resulted in the depletion of large vertebrates from ecological communities, creating what has been termed "empty forest". Defaunation differs from extinction; it includes both the disappearance of species and declines in abundance. Defaunation effects were first implied at the Symposium of Plant-Animal Interactions at the University of Campinas, Brazil in 1988 in the context of Neotropical forests. Since then, the term has gained broader usage in conservation biology as a global phenomenon.

Vulnerable species IUCN conservation category

A vulnerable species is a species which has been categorized by the International Union for Conservation of Nature as likely to become endangered unless the circumstances that are threatening its survival and reproduction improve.

In ecology, extinction debt is the future extinction of species due to events in the past. The phrases dead clade walking and survival without recovery express the same idea.

List of threatened and endangered arthropods, including insects, arachnids, and crustaceans under the United States Endangered Species Act as of October 2013.

Decline in insect populations Ecological trend

Several studies report a substantial decline in insect populations. Most commonly, the declines involve reductions in abundance, though in some cases entire species are going extinct. The declines are far from uniform. In some localities, there have been reports of increases in overall insect population, and some types of insects appear to be increasing in abundance across the world.

Endangered species (IUCN status) Species which have been categorized as very likely to become extinct in the near future

Endangered species as classified by the International Union for Conservation of Nature (IUCN), are species which have been categorized as very likely to become extinct in the near future. On the IUCN Red List, endangered is the second most severe conservation status for wild populations in the IUCN's schema after Critically endangered (CR). In 2012, the IUCN Red List featured 3,079 animal and 2,655 plant species as endangered (EN) worldwide. The figures for 1998 were 1,102 and 1,197 respectively.

References

  1. Mark A. Deyrup and Thomas Eisner (2001). "Snapshots at the Edge of a Cliff". Wings. 24 (2).CS1 maint: uses authors parameter (link)
  2. 1 2 Southern Appalachian Information Node: Resources about Arthropods
  3. 1 2 3 Redak, Richard (2000). "Arthropods and Multispecies Habitat Conservation Plans: Are We Missing Something?". Environmental Management. 26 (Supplement 1): S97–S107. doi:10.1007/s002670010065.
  4. Chad Arment, Cryptozoology: Science and Speculation, 393 pages. ISBN   1-930585-15-2 (2004)
  5. Anna Thanukos, The Arthropod Story, University of California, Berkeley
  6. Jaboury Ghazoul and R. Uma Shaanker, Sex in Space: Pollination among Spatially Isolated Plants, Biotropica: Volume 36, Issue 2, Page 128, June, 2004
  7. Brigette Michele Braschler, (2005) Effects of Experimental Small-Scale Grassland Fragmentation on the Population Dynamics of Invertebrates PhD Thesis, University of Basel