The Global Centre for Risk and Innovation (GCRI)
Species populations and the genetic variation within them are the raw material of every ecosystem and of its capacity to adapt. Extinction is the last step of a long decline, and much of the loss happens earlier, as populations shrink, fragment and lose genetic diversity. This page sets out how populations and extinction risk are observed, how genetic diversity is monitored, and how uneven evidence across species and regions shapes what can be concluded.
GCRI · Established · service level R0
Species extinction risk is the probability that a species will disappear within a given time, assessed by the IUCN Red List from population size, decline and range. Extinction is the last step of a long decline: populations shrink, fragment and lose genetic diversity first. Evidence is uneven across species and regions, which limits what can be concluded.
Mountain ranges, deserts, wetlands, glaciers and reefs, and how remote each division is from large cities, shown for Southern Africa as an example geography for this subject.
The working screen behind this subject: its structure, terms and states. Names are placeholders and values illustrative.
Species and genetic diversity · Wetland complex · Accounting year 3
| Water level regime | 0.7 | 0.6 | 1.0 |
| Native vegetation cover | 0.5 | 0.4 | 1.0 |
| Invasive species pressure | 0.3 | 0.4 | 0.0 |
| Connectivity | 0.5 | 0.6 | 1.0 |
Species populations and genetic diversity. The dossier below sets out how the risk develops, what is measured, where the data come from, how it is modelled and who decides.
IPBES identifies five direct drivers of loss: change in land and sea use, direct exploitation, climate change, pollution and invasive alien species. Their weight differs by group and region, and most declining species face several at the same time.
As a population shrinks, inbreeding, loss of genetic variation and demographic chance raise its extinction risk further. A population can persist for decades below a viable size, leaving an extinction debt that is paid later.
Fragmentation isolates populations and cuts gene flow. Genetic diversity can fall faster than numbers, reducing the capacity to adapt to disease and a changing climate, including in crop wild relatives and traditional livestock breeds.
Removing top predators, pollinators, seed dispersers or habitat-forming species changes the abundance of many others. Hunting out large seed dispersers alters tree composition and carbon storage; overfishing of grazers lets algae smother reefs.
Each term as this page uses it. Where a standard-setting body defines the term, the wording follows that body.
| Term | Definition |
|---|---|
| IUCN Red List | The global assessment of species' extinction risk, with categories from Least Concern to Extinct based on standard criteria. |
| Red List Index | An index of how the overall extinction risk of a set of species changes over time; SDG indicator 15.5.1. |
| Effective population size | The size of an idealised population that would lose genetic diversity at the same rate as the real one. |
| Living Planet Index | An index of average change in monitored vertebrate population abundance relative to a baseline. |
Each indicator carries its unit, its cadence, the kind of source behind it and the evidence label a value would carry. No values are shown: a programme supplies them under its own authority.
| Indicator | Unit | Cadence | Source type | Label |
|---|---|---|---|---|
| Red List Index | dimensionless index of aggregate extinction risk | per reassessment cycle | IUCN Red List assessments | OFFICIAL |
| Living Planet Index | index relative to a baseline year | biennial | Compiled vertebrate population time series | ESTIMATED |
| Species Habitat Index | percent of suitable habitat retained relative to baseline | annual | Remote sensing with species range models | MODELLED |
| Populations above the effective size threshold | percent of populations assessed | per assessment | Census and genetic estimates of effective population size | ESTIMATED |
| Georeferenced occurrence records | count of records per taxon and grid cell | continuous | Natural history collections and observation networks | OBSERVED |
| Threatened species in a site or range | count of species by Red List category | per assessment | IUCN range maps intersected with sites | ESTIMATED |
| Abundance trend of monitored populations | percent change per year | annual | Standardised surveys such as breeding bird counts | OBSERVED |
The topic as a computational graph: named sources feed the methods, an evidence review gates the outputs, and the decisions stay with the authorities that hold them.
Fig. 02Nodes carry their type, two metric rows and a state; connectors show what feeds what; dashed frames name the owners; the timeline is the cadence. Design of the pipeline, not a record of a run.
Named public datasets and institutional records, each with its licence class. Sources by agreement are used only under their terms and never republished.
| Source | What it gives | Licence class |
|---|---|---|
| IUCN Red List of Threatened Species | Extinction-risk assessments, range maps, threats and conservation actions | Free for non-commercial use, terms of use |
| Global Biodiversity Information Facility (GBIF) | Species occurrence records from collections, surveys and citizen science | CC0, CC BY or CC BY-NC per dataset |
| Living Planet Index database | Vertebrate population time series compiled from published sources | Free for non-commercial use, terms of use |
| BioTIME | Assemblage time series of species abundance at fixed locations | Terms per study, mostly open with attribution |
| INSDC sequence archives and the Barcode of Life Data System | Genetic sequences and DNA barcodes for identification and diversity estimates | Public, no restrictions on INSDC; open with attribution on BOLD |
| eBird Basic Dataset (Cornell Lab of Ornithology) | Checklist-based bird observations with effort information | Free for non-commercial use, terms of use |
| National biodiversity monitoring schemes | Standardised counts such as breeding bird and butterfly monitoring | Public records, terms per scheme |
Biodiversity Nexus prepares evidence. The decisions below are taken by the authorities named, under their own rules, and never by the platform.
| Who decides | The question | Evidence this page serves |
|---|---|---|
| Environment ministries and CBD national focal points | Which species and populations need recovery action, and how genetic diversity is reported in the national strategy | Red List status, population trends, effective size estimates where they exist |
| Wildlife and protected-area agencies | Where to survey, protect or translocate, and which threats to address first | Distribution models, threat maps, record gaps |
| CITES management and scientific authorities | Whether trade in a species is non-detrimental to its survival in the wild | Population status and trend, harvest and trade records, the uncertainty in each |
| Infrastructure developers and their lenders | Whether a site holds critical habitat for threatened or range-restricted species | Red List ranges, Key Biodiversity Areas and occurrence records at the site, with gaps stated |
Experts studying species and genetic diversity return to a common set of questions.
Populations decline when habitat is lost or fragmented, when individuals are harvested faster than they reproduce, when invasive species or diseases arrive, or when the climate moves outside their tolerance. Small, isolated populations then face further risks of their own: random fluctuations in births and deaths, inbreeding, and the loss of rare genetic variants through drift. These processes can carry a population towards extinction even after the original pressure has eased, a pattern often described as an extinction debt.
Genetic diversity matters because it sets the range of responses available to a population when conditions change. Domesticated species face the same issue: narrowing the genetic base of crops and livestock can raise productivity while increasing vulnerability to a single pest or disease. Loss of a functionally important species, such as a dominant grazer or a pollinator, can change an entire ecosystem.
Repeated counts, transects, camera traps and citizen science records reveal trends. Coverage is uneven, biased towards well-studied groups and accessible places.
Standard criteria combine population size, decline and range. Many species lack the data to be assessed at all.
DNA fragments in water or soil can detect species without seeing them. Detection is not abundance, and reference libraries are incomplete.
Genetic sampling estimates effective population size and connectivity. It is still rare outside a few species, and its analysis draws on spatial statistics.
The current service level is R0: information and enquiries. An enquiry receives a reference and names the next step; applications, payments, compute allocations and registrations open only when their team, terms and review capacity exist.