Biodiversity
What we're losing and why it matters
Description
Earth currently hosts somewhere between five and ten million species of multicellular life, though only about two million have been formally described and named. The total includes vertebrates (roughly 70,000 described species), invertebrates (around a million described, with many more waiting), plants (390,000 described), fungi (150,000 described with perhaps three to six million total), and uncountable prokaryotes (bacteria and archaea) that form the metabolic base of every ecosystem. This is the result of roughly 3.8 billion years of evolution, punctuated by five mass extinctions that each wiped out 50-95% of existing species and reset the evolutionary trajectory. The sixth mass extinction is probably underway now, caused by humans, and the pace may be the fastest in Earth's history.
The word biodiversity was coined in the mid-1980s to describe this total variety of life. It covers three levels: genetic diversity within species, species diversity within ecosystems, and ecosystem diversity across regions. All three levels are declining measurably, though the specific rates and patterns vary across taxonomic groups and regions. The Living Planet Index, which tracks populations of vertebrate species globally, has shown a roughly 70% average decline in wildlife population sizes since 1970. The IUCN Red List classifies over 40,000 species as threatened with extinction, a number that has grown steadily as more species are assessed and conditions worsen.
Why biodiversity matters beyond the intrinsic question of whether species have value in themselves has accumulated substantial scientific evidence over the past several decades. Diverse ecosystems are more productive, more resilient to disturbance, and more valuable to human economies than simplified ones. Specific species provide specific services pollination, pest control, water filtration, soil formation, disease regulation that are difficult or impossible to replace. The pharmaceutical and agricultural industries depend on biodiversity as a source of compounds and genetic material. The aesthetic, cultural, and psychological value of natural diversity is substantial even if harder to quantify. The loss is real, the consequences are substantial, and the response so far has been inadequate.
The question we're asking: what is biodiversity, what are we losing, and why does it matter?
What we'll see: what biodiversity includes, the current loss, the specific services it provides, and the response.
Table of contents
01What biodiversity includes
Species diversity is the most commonly measured form. The number of species in a given area, along with the evenness of their abundances, provides a basic measure of biological variety. The Amazon rainforest, per unit area, contains roughly ten times more plant and animal species than a temperate forest of equivalent size. Coral reefs, covering less than one percent of ocean surface, harbor roughly a quarter of all marine species. Tropical wetlands, remnant grasslands, and certain mountainous regions are similarly disproportionate reservoirs of species. Most biodiversity is concentrated in a relatively small set of specific ecosystems a fact that has substantial implications for conservation priorities.
Genetic diversity within species is less visible but equally important. Each species includes populations with specific genetic variations adapted to specific local conditions. This within-species variation is what allows species to adapt to changing environments over time. When species decline in population size or are restricted to smaller geographic ranges, their genetic diversity declines, and their ability to adapt to future changes is reduced. The specific problem is that even when a species is not technically extinct, it may have lost substantial genetic diversity that once allowed it to thrive. Conservation genetics tracks these patterns and increasingly emphasizes preserving specific populations rather than just species.
02The current loss
The rate of current species extinction has been estimated at roughly 100 to 1,000 times the natural background rate — the rate at which species would go extinct in the absence of human influence. The specific estimates vary because extinction is hard to measure precisely, but the direction and order of magnitude are consistent across studies. This is the rate at which the previous mass extinctions unfolded. The current event is not yet at the scale of the Cretaceous-Paleogene extinction (which killed the dinosaurs) or the Permian-Triassic extinction (the most severe in Earth's history), but it is on a trajectory that could approach these if current trends continue.
The causes of current biodiversity loss are specific and well-documented. Habitat destruction conversion of forests, grasslands, and wetlands to agriculture and urban uses is the largest driver. Climate change is increasingly important and will become dominant if warming exceeds certain thresholds. Direct exploitation (overhunting, overfishing, wildlife trade) causes substantial declines in specific species. Invasive species, pollution, and specific diseases add to the pressures. These drivers often interact — a habitat reduced by deforestation is more vulnerable to climate disruption and invasive species, creating cumulative effects that can tip ecosystems into collapse.
03The services biodiversity provides
Pollination is the most commonly cited ecosystem service. Roughly 75% of flowering plants and 35% of global crop production depend on animal pollinators, primarily insects. The economic value of pollination has been estimated at hundreds of billions of dollars annually. Declines in pollinator diversity and abundance threaten specific crops in specific regions almonds, blueberries, apples, and many others have shown measurable yield reductions in areas with reduced pollinator populations. Commercial honeybees, sometimes proposed as a substitute for wild pollinators, are themselves in decline and cannot fully replace the specific pollination services that diverse wild pollinators provide.
Pest control by natural predators is another substantial service. Insect-eating birds, bats, spiders, predatory insects, and various other species suppress pest populations that would otherwise damage crops and spread disease. Studies in specific agricultural systems have shown that reducing predator diversity through habitat simplification leads to pest outbreaks that require more pesticides. The specific economic value of natural pest control has been estimated in the hundreds of billions of dollars. Substituting chemical pesticides is possible but increasingly expensive, produces specific environmental harms, and faces resistance evolution in the pests.
04The response
Protected areas have been the traditional conservation approach. Roughly 17% of land surface and 8% of ocean area is now formally protected in some form, though enforcement varies and protection on paper often does not prevent actual degradation. The 30x30 initiative a commitment by many countries to protect 30% of land and ocean by 2030 would represent a substantial expansion if actually implemented. Protected areas are most effective when they are large, well-connected, and properly enforced. Small isolated protected areas have limited effectiveness against the larger-scale pressures driving biodiversity loss.
Species-specific conservation programs have produced some notable successes. Specific species like the Bald Eagle (US), the Giant Panda (China), and the Mountain Gorilla (Africa) have recovered substantially from near-extinction through targeted programs. These successes typically involve habitat protection, reduced hunting pressure, captive breeding, and sometimes specific reintroduction efforts. The specific conditions under which species recover are understood; scaling the approach to the thousands of species currently threatened is the challenge. Resources are finite, and prioritization requires difficult choices about which species receive intensive conservation effort.
05Conclusion
Biodiversity loss is one of the major environmental challenges of the Anthropocene, alongside climate change with which it interacts substantially. The current rate of species loss is orders of magnitude above natural baseline, and the specific trajectory, if continued, will produce an event comparable to previous mass extinctions. The causes are well understood — habitat destruction, climate change, overexploitation, invasive species, pollution and the responses that would work are known, even where they remain politically difficult to implement. The specific gap between the scale of the problem and the scale of response is substantial.