Biodiversity

• 1. Defining Biological Variety

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  A forest in North Saskatchewan holds fungi, leaf lichens, and mosses that illustrate the concept of biodiversity. Biologists define this term as the total variety of genes, species, and ecosystems within a region. This definition unifies traditional types of biological diversity into one view. Taxonomic diversity usually measures at the species level. Ecological diversity often views ecosystem interactions. Morphological diversity stems from genetic differences. Functional diversity measures disparate species functions like feeding mechanisms or motility. The Food and Agriculture Organization defined biodiversity in 2019 as variability among living organisms and their ecosystems. The World Health Organization updated its website to describe it as variability among all sources of life. Estimates by Mora et al. in 2011 suggest approximately 8.7 million terrestrial species exist. They also note about 2.2 million oceanic species. These figures represent lower bounds for prokaryotic diversity. Other estimates include 220,000 vascular plants and 0.7 to 1 million marine species. Insect populations range between 10 and 30 million species. Bacteria numbers vary from 5 to 10 million. Fungi counts sit between 1.5 and 3 million. Only 0.075 million fungal species had been documented by 2001. Mite species reach around 1 million. Microbial species remain unreliable due to limited data. The Global Ocean Sampling Expedition increased genetic diversity estimates between 2004 and 2006. Many extant species may vanish before scientists even describe them. Birds and mammals receive the most study attention within the Animalia group. Fishes and arthropods remain the least studied animal groups.

• 2. Geographic Distribution Patterns

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  Rainforests covering less than one-fifth of Earth's land hold about half the world's species. Diversity measures higher in the tropics due to warm climates and high primary productivity near the equator. Latitudinal gradients show greater species richness at lower latitudes compared to poles. Yasuní National Park in Ecuador exemplifies regions with wet climates that foster particularly high biodiversity. The Cape Floristic Region stands out as a localized hotspot of life forms. Terrestrial biodiversity reaches up to 25 times greater levels than oceanic diversity. Forests harbor most terrestrial life on our planet. They provide habitats for 80 percent of amphibian species and 75 percent of bird species. Sixty-eight percent of mammal species live within forest environments. About 60 percent of all vascular plants grow in tropical forests. Mangroves create breeding grounds for fish and shellfish while trapping sediments. These actions protect seagrass beds and coral reefs from adverse effects. Forests span around 4 billion acres, nearly a third of Earth's land mass. One billion hectares are covered by primary forests. Over 700 million hectares of woods receive official protection status. Temperate regions support relatively few animal and plant species with large geographical distributions. Montane forests in Africa, South America, and Southeast Asia host many species with small ranges. Lowland forests in Australia, coastal Brazil, the Caribbean islands, Central America, and insular Southeast Asia contain diverse life. Areas with dense human populations like Europe, Bangladesh, China, India, and North America show less intact biodiversity. Northern Africa, southern Australia, coastal Brazil, Madagascar, and South Africa face striking losses in biodiversity integrity. Colombia holds the highest rate of species per area unit worldwide. It contains over 1,900 bird species, more than Europe and North America combined. Indonesia's 17,000 islands cover vast areas containing 10 percent of flowering plants and 12 percent of mammals. These islands also hold 17 percent of reptiles, amphibians, and birds alongside nearly 240 million people. Rev. Gilbert White observed in 1768 that districts producing the most variety were often the most examined.

• 3. Evolutionary History And Extinctions

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  Life on Earth began approximately 3.5 billion years ago as microorganisms including archaea, bacteria, and protozoans. The earliest undisputed evidence dates back at least to 3.7 billion years during the Eoarchean era. Microbial mat fossils found in 3.48 billion-year-old sandstone exist in Western Australia. Graphite in 3.7 billion-year-old meta-sedimentary rocks discovered in Western Greenland provides early physical evidence. Remains of biotic life appeared in 4.1 billion-year-old rocks in Western Australia according to a 2015 study. Biodiversity grew rapidly during the Phanerozoic aeon spanning the last 540 million years. The Cambrian explosion marked a period where nearly every multicellular phylum first appeared. Recent studies suggest this diversification started earlier in the Ediacaran period. Invertebrate diversity showed little overall trend over the next 400 million years. Vertebrate diversity displayed an overall exponential trend during that same timeframe. Massive losses classified as mass extinction events occurred periodically throughout history. A significant loss happened when rainforests collapsed in the Carboniferous period. Amniotes seemed unaffected by this event but their diversification slowed around 293 million years ago. The Permian-Triassic extinction event occurred 251 million years ago and remains the worst known crisis. Vertebrates took 30 million years to recover from that specific catastrophe. The Cretaceous-Paleogene extinction event struck 66 million years ago. Dinosaurs represented many lineages at the end of the Maastrichtian stage before vanishing. Marine taxa like ammonites also became extinct around that time. Estimates suggest 5 to 50 billion species have existed on the planet. Greater than 99 percent of Earth's species went extinct prior to human evolution. Current global macroscopic species diversity estimates range from 2 million to 100 million. A best estimate places numbers near 9 million, mostly arthropods. Scientists identified a set of 355 genes from the last universal common ancestor in July 2016.

• 4. The Anthropocene Crisis

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  Human activities drive ongoing biodiversity loss and genetic diversity reduction today. This process is often called the Holocene extinction or sixth mass extinction. An estimated 30 percent of all species could vanish by 2050 according to 2007 projections. Habitat destruction for farming stands as a key reason for decreasing biodiversity levels. Climate change plays an active role in these environmental shifts. Effects of climate change impact biomes across the globe. Some studies suggest megafaunal extinctions began toward the end of the Pleistocene due to overhunting. The rate of species loss exceeds any time in human history. Extinctions occur at rates hundreds of times higher than background levels. Wildlife populations declined by an average 73 percent since 1970 per the World Wildlife Fund Living Planet Report 2024. The planet lost 58 percent of its biodiversity between 1970 and 2016 according to a 2016 study. Freshwater wildlife suffered a 76 percent decline during that period. Latin America experienced an 83 percent plummet in biodiversity. High-income countries showed a 10 percent increase but this was canceled out by losses elsewhere. Wealthy nations use five times the ecological resources of low-income countries. A 2017 study found insect biomass in Germany had dropped three-quarters in 25 years. Dave Goulson of Sussex University stated humans appear to be making land inhospitable to most life forms. In 2020, the World Wildlife Fund reported biodiversity destruction at unprecedented rates. Sixty-eight percent of examined species populations were destroyed between 1970 and 2016. Around 48 percent of monitored species experience population declines from human activity as of 2023. Only 3 percent show increasing populations. Species loss accelerates above the average basal rate since the Stone Age. Estimates place extinction rates 100 to 10,000 times faster than typical fossil record patterns. About 40 percent of assessed species face threatened extinction status today. Ninety-two hundred fifty-one species were considered critically endangered by late 2022.

• 5. Ecosystem Services And Human Health

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  Biodiversity provides critical support for drug discovery and medicinal resource availability. At least 50 percent of pharmaceutical compounds on the US market derive from plants, animals, or microorganisms. Eighty percent of the world population depends on medicines from nature for primary healthcare. Marine ecosystems offer chemical properties that led to treatments for cancer, viral bacteria, AIDS, and other conditions. Bioprospecting can increase biodiversity loss while violating community laws. The economic value of pollination alone reached between $2.1 billion and $14.6 billion in 2003. Robert Costanza estimated global ecosystem services worth an average of $33 trillion annually in 1997. Biodiversity's economic resources total around $150 trillion annually, roughly twice the world GDP. Losses harm global GDP by costing an estimated $5 trillion each year. Greater plant diversity increases fodder yield according to 271 experimental studies. Crop yields improve with greater plant diversity based on 575 studies. Tree diversity boosts overall wood production across 53 studies. Fish diversity enhances fishery stability through eight observational studies. Plant diversity aids carbon sequestration via 479 experiments. Soil nutrient remineralization improves with diverse plant life according to 103 studies. Natural pest enemies reduce herbivorous populations based on two reviews. Wetland ecosystems filter water and buffer coastal communities against storm surges. Species most likely to disappear often buffer infectious disease transmission. Surviving species tend to increase disease transmission risks like West Nile Virus or Lyme disease. Dietary health and nutrition security rely heavily on biodiversity. Social and psychological well-being connect directly to natural environments. Rising sea levels pose disaster risks that wetlands help mitigate.

• 6. Conservation Strategies And Policy

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  The target of protecting 30 percent of land and oceans by 2030 was adopted at the 2022 United Nations Biodiversity Conference. Almost 200 countries signed this agreement in December 2022. At adoption time, 17 percent of land territory and 10 percent of ocean territory were protected. Over 238,563 designated protected areas exist worldwide covering 14.9 percent of Earth's surface. South America holds the highest share of forests in protected areas at 31 percent. Approximately 50 million hectares of European forest land are protected for biodiversity purposes. The EU Biodiversity Strategy for 2030 aims to plant 3 billion trees by 2030. It plans to restore at least 25,000 kilometers of rivers to free-flowing states. Pesticide use reduction targets a 50 percent cut by 2030. Organic farming will make up 25 percent of EU agriculture by 2030. The strategy allocates €20 billion per year to these issues. Natura 2000 benefits alone generate €200 to €300 billion annually in Europe. The International Union for Conservation Nature defines National Parks as Category II protected areas. Wildlife sanctuaries serve as shelters or temporary rehabilitation centers for animals unable to survive independently. Forest reserves sometimes grant hunting rights to communities living on fringes. The Convention on Biological Diversity gives sovereign national rights over biological resources. Countries commit to conserve biodiversity and develop sustainable resources. Access and Benefit Sharing Agreements establish fair agreements between source countries and collectors. India passed the Biological Diversity Act in 2002 for conservation efforts. Citizen science enables public participation in research through platforms like iNaturalist and eBird. Nearly half of occurrence records shared through GBIF networks come from volunteer contributions.