The Sixth Extinction Signal Is Already in the Data
Vertebrate populations have declined 69 percent since 1970. Insect biomass is collapsing in monitored regions. The biodiversity crisis is quieter than climate change but possibly more severe.
Signal
The World Wildlife Fund's Living Planet Report, published in October 2022, documented a 69 percent average decline in monitored vertebrate wildlife populations between 1970 and 2018. The monitoring is not comprehensive — it covers approximately 5,000 species of amphibians, birds, fish, mammals, and reptiles out of millions of animal species — but the scale of the documented decline is large enough that measurement bias cannot plausibly explain it.
The insect data is more limited but even more alarming. A 2019 paper in Biological Conservation synthesized existing literature on insect population trends and estimated that 40 percent of insect species are in decline, that total insect biomass is declining at approximately 2.5 percent annually, and that a third of insect species are threatened with extinction on current trajectories. A 2017 study of protected nature reserves in Germany found a 75 percent decline in total flying insect biomass over 27 years.
Insects are not charismatic megafauna; their decline does not generate the public response that lions or elephants or tigers would. They are, however, foundational to the ecological systems that provide the services — pollination, decomposition, nutrient cycling, pest control — that agriculture and human food systems depend on.
Interpretation
The biodiversity crisis has several drivers that operate simultaneously and interact in ways that make them difficult to address independently.
Habitat loss — primarily from agricultural expansion, urban development, and deforestation — is the dominant driver of terrestrial species loss. Human land use now covers approximately 50 percent of the Earth's ice-free land surface; the remaining natural areas are fragmented in ways that reduce their carrying capacity for biodiversity.
Climate change is an accelerating driver: species are being pushed out of their historical range by warming, drought, and changed precipitation; some are able to track their climate niche by moving poleward or to higher elevation; many are not, either because habitat barriers prevent movement or because they move more slowly than climate change is occurring.
Pollution — particularly pesticide use in agricultural systems — is the primary driver of insect decline. Neonicotinoid insecticides, used as seed coatings on most major commodity crops, have been documented to cause sublethal neurological effects in bees, disrupting navigation, learning, and reproduction at concentrations well below those that cause acute mortality. Their persistence in soil means that their effects extend beyond the treated crop.
Scenario
Scenario A — the ecosystem services disruption scenario — involves continued biodiversity decline at current rates producing measurable disruption to agricultural systems within 15-20 years: reduced pollination of crops dependent on wild and managed pollinators, increased pest pressure as natural pest control mechanisms decline, reduced soil health as decomposer and nutrient cycling communities thin.
Scenario B — the ecological collapse scenario — involves threshold effects in specific ecosystems — trophic cascades triggered by the removal of keystone species, transitions from diverse to simplified ecosystems — that produce rapid, nonlinear changes rather than gradual decline. This scenario is not well-predicted by current models because threshold effects are by definition difficult to anticipate before they occur.
Scenario C — the managed transition scenario — involves the deployment of significant conservation investment in biodiversity-critical regions, the reform of agricultural systems to reduce pesticide intensity, and the establishment of ecological corridors that allow species range shifts in response to climate change. This scenario is technically feasible; its political economy is extremely challenging.
Probability
Metaculus forecasts a 71 percent probability that the global extinction rate will be documented at more than 100 times the pre-industrial background rate before 2030 — a threshold that has been described as mass extinction territory by some paleontologists. The current estimated extinction rate is already in this range; the probability reflects confirmation through systematic monitoring rather than current trends.
Kalshi was trading a contract on whether the Kunming-Montreal Global Biodiversity Framework target — protecting 30 percent of land and ocean globally by 2030 — will be on track to be met based on 2028 assessment data at 22 percent. The targets are ambitious relative to current trajectories; the funding commitments that would enable their achievement have not materialized.
Indicators to Watch
— IPBES Biodiversity Assessments: annual updates to the Intergovernmental Science-Policy Platform on Biodiversity and Ecosystem Services provide the most authoritative synthesis of trend data — Neonicotinoid regulatory status: EU restrictions on neonicotinoids since 2018 provide a natural experiment in whether regulatory intervention arrests insect decline; US EPA's continuing neonicotinoid review signals domestic policy direction — Amazon deforestation real-time monitoring: Brazil's INPE system provides monthly deforestation data; the Amazon's tipping point (estimated at 20-25% deforestation) for transition from rainforest to savanna is a global biodiversity and carbon threshold — Protected area effectiveness monitoring: the difference between nominally protected areas and effectively protected areas is large; systematic monitoring of protection quality is a leading indicator of conservation outcomes
Daniel Osei is a staff writer at The Auguro covering climate, energy, and environmental policy.