Sustainability & Environment (Agri-Food Systems) · Natural Resources & Biodiversity · also Conservation Biology, Biodiversity and Conservation, Wildlife and Biodiversity Conservation
What biodiversity is, how it is measured, why it is being lost and how it is conserved, from IUCN Red List categories and protected areas to the Kunming-Montreal Global Biodiversity Framework.
In the exams: ICAR AICE subject 71 Unit 2 (whole unit); GATE ES Section 8 (biodiversity); UGC NET Unit 3; UPSC CSE Prelims environment (heavily asked)
Biodiversity — the variety of genes, species and ecosystems — is the living fabric on which agriculture, forestry, fisheries and human well-being depend, and it is being lost faster than at any time in human history. This subject explains what biodiversity is and how it is measured, where it is concentrated, why it matters, what is driving its loss, and how it is conserved, from the population genetics of small populations to protected area networks, seed banks and international agreements.
It covers the levels of biodiversity; alpha, beta and gamma diversity and the main indices; biogeographic realms and hotspots; the values of biodiversity; the drivers of loss identified by IPBES; island biogeography and species-area relationships; population viability and minimum viable population; IUCN Red List categories and criteria; in-situ conservation in protected areas and biosphere reserves; ex-situ conservation in zoos, botanic gardens and gene banks; management of invasive alien species; and the Convention on Biological Diversity, the Kunming-Montreal framework, national laws and access and benefit-sharing. Treaty details are in environmental-law-policy; forest ecology field methods are in the forestry subjects forest-ecology and wildlife-biology-ecology, and protected area management in wildlife-management-protected-areas; the economics of valuing biodiversity are in the Agribusiness subject natural-resource-environmental-economics; and the services biodiversity provides to farming are in ecosystem-services-pollinators.
Biodiversity is a whole unit (Unit 2) of the ICAR AICE Environmental Sciences syllabus, part of GATE ES Section 8 and GATE Ecology and Evolution, a unit of UGC NET Environmental Sciences, and one of the most heavily examined topics in the UPSC Civil Services preliminary examination. Figures on species numbers, protected area coverage and threatened species change as assessments are updated; those given here are cited with their source year.
The Convention on Biological Diversity defines biological diversity as the variability among living organisms from all sources, including terrestrial, marine and other aquatic ecosystems and the ecological complexes of which they are part; this includes diversity within species, between species and of ecosystems. These three levels are the standard framework. Genetic diversity is the variety of genes and alleles within and among populations of a species; it is measured as heterozygosity, allelic richness and differentiation among populations, and it underpins adaptation to changing environments, resistance to disease and the breeding of crops and livestock. Species diversity is the number and relative abundance of species in an area. Ecosystem diversity is the variety of habitats, biological communities and ecological processes — forests, grasslands, wetlands, coral reefs, agricultural landscapes — and of the interactions among them. Some authors add functional diversity (the range of traits and roles species play) and phylogenetic diversity (the evolutionary history represented by a set of species), which can matter more for ecosystem functioning than species counts.
About 2.1 million species have been formally described, most of them insects and other invertebrates, while estimates of the total number of eukaryotic species on Earth range widely; one frequently cited estimate (Mora and colleagues, 2011) is about 8.7 million, of which most are undescribed, and estimates for bacteria and archaea are far higher and very uncertain. Diversity is unevenly distributed: species richness generally increases from the poles to the tropics (the latitudinal diversity gradient), tropical forests and coral reefs are exceptionally rich, and a small number of 'megadiverse' countries — seventeen in a widely used list including Brazil, Colombia, Indonesia, India, China, Mexico and Australia — contain most of the world's species. India, with about 2.4 % of the world's land area, harbours an estimated 7–8 % of recorded species, including many endemic plants, amphibians and reptiles in the Western Ghats and the north-east.
Agricultural biodiversity — the variety of crops, varieties, livestock breeds, crop wild relatives, soil organisms, pollinators and natural enemies in farming systems — is a distinct and threatened part of biodiversity. Nikolai Vavilov identified centres of origin of cultivated plants where crop diversity is concentrated, including the Hindustan centre (rice, sugar cane, many pulses and vegetables) and the Indo-Malayan centre. Modern agriculture has narrowed this diversity: a handful of crops provide most of humanity's calories, and traditional landraces and local livestock breeds have been replaced by uniform high-yielding types, reducing options for adaptation (genetic erosion). Conservation of plant genetic resources combines on-farm (in-situ) conservation by farmers and ex-situ gene banks (chapter 10); the forestry track's conservation-biology-genetic-resources subject covers forest genetic resources, and the agroecology and agrobiodiversity subjects of this track cover functional diversity on farms.
Whittaker distinguished diversity at different spatial scales. Alpha diversity is the diversity within a particular site or habitat; gamma diversity is the total diversity of a landscape or region comprising several sites; and beta diversity is the change in species composition between sites, reflecting turnover along environmental gradients. In Whittaker's multiplicative formulation, beta = gamma ÷ mean alpha: if a region contains 60 species and its sites average 20 species each, beta diversity is 3, meaning the region holds the equivalent of three completely distinct communities. Additive partitioning (gamma = alpha + beta) is also used. Beta diversity matters for conservation planning because protecting several sites with different species gives more regional diversity than protecting several similar sites. Similarity between two sites is measured with presence–absence indices: the Jaccard index J = c ÷ (a + b − c) and the Sørensen index = 2c ÷ (a + b), where a and b are the species counts of the two sites and c the number shared.
Species richness (S) is the simplest measure but depends strongly on sampling effort; richness estimators correct for unseen species, for example Chao1 = S_obs + F1² ÷ (2F2), where F1 and F2 are the numbers of species seen exactly once and twice, and rarefaction compares samples standardised to the same number of individuals. Indices that combine richness and evenness include the Shannon index, H' = −Σ p_i ln p_i, where p_i is the proportion of individuals belonging to species i, and Simpson's index, D = Σ p_i², which is the probability that two individuals drawn at random belong to the same species (a dominance measure); diversity is then expressed as 1 − D or 1/D. For three species with proportions 0.5, 0.3 and 0.2, H' = 1.030, D = 0.38 and Simpson's diversity 1 − D = 0.62. Pielou's evenness J' = H' ÷ ln S compares observed H' with its maximum when all species are equally abundant (here 0.94). Other indices include Margalef's richness, (S − 1) ÷ ln N, and Menhinick's, S ÷ √N. Hill numbers unify these as 'effective numbers of species' of different orders, which behave intuitively (doubling when two equally diverse, completely distinct communities are combined).
Data come from standardised sampling: quadrats and transects for plants, point counts and transects for birds, pitfall traps and pan traps for insects, camera traps and occupancy surveys for mammals, and increasingly environmental DNA (eDNA) metabarcoding, which detects species from traces of DNA in water or soil. Field methods for forests and wildlife, including the importance value index, line transects and mark-recapture, are taught in the forestry track subjects forest-ecology and wildlife-biology-ecology. Large-scale monitoring uses indicators such as the Living Planet Index (trends in vertebrate populations), the Red List Index (trends in extinction risk, chapter 8), biodiversity intactness indices and ecosystem extent maps from remote sensing. Every index summarises information and loses some: two communities can have the same Shannon index with entirely different species, so indices should be used alongside lists of species and their conservation status.
Biogeography studies the distribution of species across space and time. Alfred Russel Wallace (1876) divided the world into six zoogeographic regions — Palaearctic, Nearctic, Neotropical, Ethiopian (Afrotropical), Oriental (Indomalayan) and Australian — based on animal distributions; Udvardy's (1975) system of biogeographic realms adds Oceania and Antarctica and subdivides realms into biogeographic provinces. Boundaries reflect long histories of continental drift and isolation: Wallace's line, through the Lombok and Makassar straits in Indonesia, separates the Asian and Australian faunas. Ecoregions — relatively large units of land or water containing distinct assemblages of species and communities — are widely used for conservation planning. India lies mainly in the Indomalayan realm, with Palaearctic elements in the trans-Himalaya; Rodgers and Panwar (1988) divided it into ten biogeographic zones: Trans-Himalaya, Himalaya, Desert, Semi-Arid, Western Ghats, Deccan Peninsula, Gangetic Plain, North-East, Islands and Coasts.
Norman Myers introduced the concept of biodiversity hotspots in 1988 to prioritise conservation where both irreplaceability and threat are high. Under the criteria adopted by Conservation International, a region qualifies as a hotspot if it contains at least 1500 species of endemic vascular plants (more than 0.5 % of the world's total) and has lost at least 70 % of its original primary vegetation. Myers and colleagues (2000) identified 25 hotspots covering 1.4 % of the land surface but containing 44 % of vascular plant species and 35 % of terrestrial vertebrate species as endemics; the list has since grown to 36. Four hotspots include parts of India: the Himalaya, Indo-Burma, the Western Ghats and Sri Lanka, and Sundaland (through the Nicobar Islands). Hotspot prioritisation has been criticised for focusing on plants and endemism, neglecting species-poor but threatened ecosystems, wilderness areas, marine systems and ecosystem services; complementary schemes include high-biodiversity wilderness areas, Key Biodiversity Areas (sites contributing significantly to the global persistence of biodiversity, identified under an IUCN standard), Important Bird and Biodiversity Areas, and Global 200 ecoregions.
Endemic species are restricted to a particular area; their concentration in islands, mountains and isolated habitats reflects speciation in isolation, and makes these places irreplaceable. The Western Ghats, for example, have high endemism among amphibians, freshwater fish and flowering plants. Systematic conservation planning uses principles of complementarity (adding sites that contain species not yet protected), irreplaceability, representativeness (covering all ecosystem types) and efficiency (achieving targets at minimum cost or area), often with optimisation software and spatial data. These principles inform national protected area networks and the global '30 by 30' target (chapter 9), which is meant to cover areas of particular importance for biodiversity, not simply any 30 % of land.
Biodiversity is valued in several ways. Direct use values come from consumptive uses — food, timber, fuelwood, fibre, fodder, medicines (many drugs derive from natural products, such as aspirin from willow, quinine from cinchona and the anticancer drugs vincristine and vinblastine from the Madagascar periwinkle) — and productive and non-consumptive uses such as ecotourism, recreation and research. Indirect use values come from ecosystem functions and services: pollination, pest control, soil formation, water purification, climate regulation and flood control (see ecosystem-services-pollinators). Option value is the value of keeping biodiversity available for possible future use, such as genes for crop breeding or undiscovered medicines. Together with non-use values, these make up the total economic value framework; the methods for estimating them in money (market prices, contingent valuation, travel cost, hedonic pricing, benefit transfer) are taught in the Agribusiness subject natural-resource-environmental-economics.
Non-use values arise even if people never use biodiversity. Existence value is the satisfaction of knowing that a species or ecosystem exists, such as tigers or whales; bequest value is the value of conserving it for future generations; and altruistic value concerns its availability to others now. Beyond these anthropocentric values, many ethical traditions hold that species and ecosystems have intrinsic value — value in themselves, independent of usefulness to people. The CBD's preamble affirms the intrinsic value of biological diversity alongside its ecological, genetic, social, economic, scientific, educational, cultural, recreational and aesthetic values. Religious and cultural traditions, including the protection of sacred groves and sacred species in India and many other countries, express such values in practice.
The Intergovernmental Science-Policy Platform on Biodiversity and Ecosystem Services (IPBES) Values Assessment (2022) found that policy decisions usually prioritise a narrow set of market values and neglect the diverse values of nature held by different people — instrumental, intrinsic and relational values, the last describing the importance of meaningful relationships between people and nature, such as identity, stewardship and sense of place. It argued that recognising plural values and the worldviews of indigenous peoples and local communities is essential to transformative change. For practitioners, this means that monetary valuation can inform decisions but cannot capture all that is at stake; deliberative and participatory methods, multi-criteria analysis and recognition of rights complement it. Arguments for conservation that rely only on economic value can backfire when an alternative land use appears more profitable.
The IPBES Global Assessment (2019) concluded that nature is declining globally at rates unprecedented in human history: around one million animal and plant species are threatened with extinction, many within decades; three-quarters of the land surface and two-thirds of the ocean area have been significantly altered by human actions; and more than 85 % of wetland area present in 1700 had been lost by 2000. The current rate of global species extinction is at least tens to hundreds of times higher than the average over the past ten million years. The Living Planet Index, which tracks monitored populations of vertebrates, showed an average decline of 73 % between 1970 and 2020 in its 2024 report, with the steepest declines in freshwater populations and in Latin America and the Caribbean. Earth has experienced five mass extinctions — at the end of the Ordovician, in the Late Devonian, at the end of the Permian (the largest), at the end of the Triassic and at the end of the Cretaceous — and many scientists argue that a sixth, human-caused mass extinction is under way.
IPBES ranked five direct drivers of change in nature, in order of global impact: changes in land and sea use, direct exploitation of organisms, climate change, pollution, and invasive alien species. On land, conversion of natural ecosystems to agriculture is the dominant driver, followed by urban and infrastructure expansion; in the oceans, fishing has had the largest impact. Direct exploitation includes hunting, harvesting, logging, the wildlife trade and fishing. Climate change shifts species ranges, alters phenology (the timing of flowering, breeding and migration), and threatens coral reefs, mountain and polar species, and its importance is rising. Pollution includes nutrient runoff causing eutrophication and dead zones, pesticides affecting insects, birds and aquatic life, plastics and light and noise pollution. Invasive alien species are discussed in chapter 11. The older acronym HIPPO (habitat destruction, invasive species, pollution, human population, overharvesting) summarises similar factors.
Behind the direct drivers lie indirect drivers: demographic and economic growth, consumption patterns, trade, technology, governance, institutions and values. Agriculture is both the largest driver of biodiversity loss on land and heavily dependent on biodiversity. Expansion of cropland and pasture into forests, savannas and wetlands removes habitat (see sustainable-supply-chains); intensification simplifies landscapes, removes hedgerows and field margins, and increases fertiliser and pesticide use; drainage and irrigation alter wetlands and rivers; and homogenisation of crops and breeds erodes agrobiodiversity. Studies in Europe and elsewhere have documented large declines in farmland birds and in insect biomass, linked to habitat loss and agricultural intensification. Interactions among drivers matter: fragmented habitats leave populations more vulnerable to climate change, and nutrient pollution favours invasive species. Reversing loss therefore requires action on indirect drivers — consumption, diets, food waste, trade and subsidies — as well as on direct pressures.
One of ecology's most robust patterns is that larger areas contain more species. The species-area relationship is usually written as a power function, S = cA^z, where S is the number of species, A the area, c a constant depending on the taxon and region, and z the slope on a log-log plot. Values of z typically lie between about 0.15 and 0.35, with higher values for isolated islands and lower values for samples of contiguous mainland. A widely used rule of thumb follows: with z near 0.3, a tenfold reduction in area roughly halves the number of species (because 10^−0.3 ≈ 0.5). The relationship is used to predict species loss from habitat loss: if 90 % of a habitat is destroyed and z = 0.25, the remaining 10 % is expected eventually to hold 0.1^0.25 of the species, a loss of about 44 %. Such predictions are approximate: species-area curves derived for islands may overestimate losses where the converted landscape still supports some species ('countryside biogeography'), and losses can be delayed for decades, creating an extinction debt.
MacArthur and Wilson (1967) proposed that the number of species on an island reflects a dynamic equilibrium between immigration of new species and extinction of species already present. The immigration rate falls as the island fills with species and is lower for islands far from the mainland source; the extinction rate rises as more species are present and is higher on small islands, whose populations are smaller. The equilibrium number of species is therefore highest on large, near islands and lowest on small, far ones, and species composition turns over even when the number is stable. The theory was quickly applied to 'habitat islands' — forest fragments in farmland, mountaintops, lakes and protected areas surrounded by altered land — and to the design of reserves.
Diamond (1975) proposed reserve design principles derived from island biogeography: larger reserves are better than smaller; a single large reserve is better than several small ones of the same total area; reserves close together are better than far apart; clustered reserves are better than linear ones; reserves connected by corridors are better than unconnected ones; and compact, round reserves are better than elongated ones that maximise edge. The 'single large or several small' (SLOSS) debate showed that the answer depends on species and context: several small reserves can capture more species if they sample different habitats, and spread the risk of catastrophes. Fragmentation has effects beyond area loss: edge effects (changes in microclimate, predation and invasion near edges), isolation that reduces movement and gene flow, and loss of large-bodied and area-demanding species. Corridors and stepping stones, landscape matrix management (for example agroforestry and hedgerows) and connectivity planning are therefore central to conservation in agricultural landscapes; landscape ecology is taught further in the forestry subject landscape-ecology-ecosystem-modelling.
Small populations face risks beyond those that caused their decline. Demographic stochasticity is chance variation in births, deaths and sex ratio, which can drive very small populations extinct. Environmental stochasticity is variation in conditions such as weather, food supply and disease that affects all individuals, and catastrophes are extreme events such as fires, floods and epidemics. Genetic problems include inbreeding depression (reduced survival and reproduction from mating among relatives), loss of genetic diversity through genetic drift, and accumulation of harmful mutations. These processes can reinforce one another in an 'extinction vortex' (Gilpin and Soulé, 1986), in which a smaller population suffers more inbreeding and stochastic decline, becoming smaller still. The Allee effect — reduced per-capita growth at low density because of difficulty finding mates or cooperating — adds to the risk.
The effective population size (Ne) is the size of an idealised population that would lose genetic diversity at the same rate as the real one; it is usually much smaller than the census size because of unequal sex ratios, variation in reproductive success and fluctuations in numbers. With unequal numbers of breeding males (Nm) and females (Nf), Ne = 4NmNf ÷ (Nm + Nf): a population of 10 breeding males and 40 breeding females has Ne = 32, not 50. Inbreeding increases by ΔF = 1 ÷ (2Ne) per generation, and heterozygosity declines as Ht = H0 (1 − 1/(2Ne))^t over t generations. The '50/500 rule' (Franklin and Soulé, 1980) suggested that an effective size of at least 50 avoids severe short-term inbreeding depression and at least 500 retains long-term evolutionary potential; later work (Frankham and colleagues, 2014) argued for raising these to 100 and 1000. Genetic rescue — introducing individuals from other populations to restore diversity — has improved fitness in many inbred populations, such as the Florida panther.
Shaffer (1981) defined a minimum viable population (MVP) as the smallest isolated population having a 99 % chance of remaining extant for 1000 years despite the foreseeable effects of demographic, environmental and genetic stochasticity and natural catastrophes. There is no universal MVP; estimates vary widely among species and situations, though reviews have suggested that thousands of adults are often needed for long-term persistence. Population viability analysis (PVA) estimates the probability of extinction or decline of a population over a time horizon under specified conditions, using demographic data (survival, fecundity, carrying capacity), their variability and, in some models, genetics. Simple models project population size as N_t = N_0 λ^t, where λ is the finite rate of increase: a population of 200 with λ = 0.95 falls to about 120 in ten years. PVA results are most useful for comparing management options — for example, the effect of reducing poaching, increasing habitat or translocating animals — rather than as precise predictions, because data are usually limited. PVA underlies IUCN Red List criterion E (chapter 8) and recovery planning for threatened species.
The IUCN Red List of Threatened Species, maintained since 1964 and based on quantitative categories and criteria since 1994 (current version 3.1, 2001), is the world's most comprehensive source on extinction risk. Species are assessed into nine categories: Extinct (EX), Extinct in the Wild (EW), Critically Endangered (CR), Endangered (EN), Vulnerable (VU), Near Threatened (NT), Least Concern (LC), Data Deficient (DD) and Not Evaluated (NE). The three threatened categories are CR, EN and VU. A species is listed in a threatened category if it meets any one of five criteria (A to E) at the relevant threshold. Tens of thousands of species are now listed as threatened, including a large share of amphibians, cycads, reef-building corals, sharks and rays, and conifers; but many groups, especially invertebrates and fungi, remain poorly assessed. The Red List Index tracks changes in aggregate extinction risk over time, and the IUCN Green Status of Species (2021) measures recovery towards a species' full ecological role.
Criterion A is population reduction: for reductions whose causes are reversible, understood and have ceased (A1), the thresholds are at least 90 % for CR, 70 % for EN and 50 % for VU over ten years or three generations, whichever is longer; for other reductions (A2–A4), they are 80 %, 50 % and 30 %. Criterion B is restricted geographic range combined with fragmentation, decline or extreme fluctuations: extent of occurrence (B1) below 100 km² for CR, 5000 km² for EN and 20000 km² for VU, or area of occupancy (B2) below 10, 500 and 2000 km² respectively. Criterion C is a small population with continuing decline: fewer than 250, 2500 and 10000 mature individuals. Criterion D is a very small or restricted population: fewer than 50 mature individuals for CR, 250 for EN and 1000 for VU (D1), or for VU a very restricted area of occupancy, typically under 20 km², or five or fewer locations (D2). Criterion E is a quantitative analysis showing a probability of extinction in the wild of at least 50 % within ten years or three generations (CR), 20 % within twenty years or five generations (EN), or 10 % within 100 years (VU). For example, a species whose population fell by 60 % over three generations from causes still operating qualifies as EN under A2; one with 180 mature individuals qualifies as EN under D.
The Red List informs conservation priorities, environmental impact assessment (IFC Performance Standard 6 uses CR and EN species to identify critical habitat, see environmental-impact-assessment), national legislation, CITES listing decisions and corporate biodiversity disclosures (see sustainability-reporting-esg). Assessments are carried out by specialist groups and reviewed before publication; national and regional red lists apply the criteria with guidelines for regional application, which adjust categories for immigration from neighbouring populations. India's national lists and schedules under the Wildlife (Protection) Act (see environmental-law-policy) are legal instruments separate from the Red List: a species can be globally Least Concern but legally protected in India, or threatened globally but not scheduled. Users should cite the assessment year and criteria, because categories change as knowledge and status change.
In-situ conservation protects species in their natural habitats, maintaining ecological interactions and evolutionary processes. IUCN defines a protected area as a clearly defined geographical space, recognised, dedicated and managed, through legal or other effective means, to achieve the long-term conservation of nature with associated ecosystem services and cultural values. IUCN management categories range from strict protection to sustainable use: Ia strict nature reserve; Ib wilderness area; II national park; III natural monument or feature; IV habitat or species management area; V protected landscape or seascape; and VI protected area with sustainable use of natural resources. In 2018 the CBD added 'other effective area-based conservation measures' (OECMs) — areas outside protected areas, such as some community forests, military lands or sustainably managed sites, that deliver long-term in-situ conservation. Global coverage reached roughly 17–18 % of land and inland waters and over 8 % of the ocean by 2024, against the Kunming-Montreal target of 30 % by 2030 (see environmental-law-policy).
UNESCO's Man and the Biosphere (MAB) programme, launched in 1971, designates biosphere reserves that reconcile conservation with sustainable use. Each has a core area (strictly protected), a buffer zone (activities compatible with conservation, research and education) and a transition area (sustainable economic activities with communities). The World Network includes several hundred sites in over a hundred countries. India has 18 biosphere reserves designated nationally, of which a dozen or more are in the UNESCO network, the first being the Nilgiri Biosphere Reserve (1986, UNESCO 2000). India's protected area network under the Wildlife (Protection) Act includes national parks, wildlife sanctuaries, conservation reserves and community reserves, covering roughly 5 % of the country's area, together with tiger reserves under Project Tiger (launched 1973) and elephant reserves under Project Elephant (1992). Community conservation — sacred groves, community reserves, and the forests managed by communities under the Forest Rights Act — adds substantially to conservation outside the formal network. Management of protected areas and wildlife is covered in depth in the forestry subject wildlife-management-protected-areas.
Designation does not guarantee protection: 'paper parks' exist on maps but lack management, staff and funding. Management effectiveness evaluations (such as the Management Effectiveness Tracking Tool and India's management effectiveness evaluations of tiger reserves and protected areas) assess planning, inputs, processes, outputs and outcomes. Studies comparing protected areas with matched unprotected land show that protection often reduces deforestation, but effects vary and are smaller where pressure is low. The history of 'fortress conservation' — creating parks by excluding or evicting local people — caused injustice and conflict, and contemporary practice emphasises rights-based approaches, co-management, benefit sharing, recognition of indigenous and community conserved areas, and addressing human–wildlife conflict through compensation, insurance, barriers and land-use planning. Effective in-situ conservation also needs connectivity between protected areas and management of the surrounding landscape, including farmland.
Ex-situ conservation maintains components of biodiversity outside their natural habitats. It complements, but cannot replace, in-situ conservation, because it captures only part of genetic diversity, can cause adaptation to captivity, and loses ecological interactions. Zoos and aquaria contribute through coordinated captive breeding programmes managed with studbooks to maximise genetic diversity, research, education and reintroduction; successes include the Arabian oryx, California condor, black-footed ferret and Przewalski's horse, which were bred in captivity and returned to the wild after extinction or near-extinction in the wild. India's Central Zoo Authority coordinates conservation breeding of species such as the red panda, vultures and the pygmy hog. Botanic gardens hold living collections representing roughly a third of known plant species, conserve threatened plants and run restoration programmes. Reintroductions and translocations should follow the IUCN Guidelines for Reintroductions and Other Conservation Translocations (2013), which stress feasibility, risk assessment, addressing the causes of decline and post-release monitoring.
Seed banks store seeds under conditions that slow ageing. Orthodox seeds — the majority of crop species and many wild plants — tolerate drying and freezing; FAO genebank standards recommend drying seeds to equilibrium with low relative humidity (moisture content of roughly 3–7 % depending on species) and storing base collections at about −18 °C, where many species remain viable for decades to centuries. Harrington's rules of thumb state that, within normal storage ranges, each 1 % reduction in seed moisture content or each 5 °C reduction in storage temperature roughly doubles seed life. Recalcitrant seeds — such as those of many tropical trees, mango, cocoa and rubber — die if dried and must be conserved in field gene banks, in vitro or by cryopreservation of embryos or tissues in liquid nitrogen at −196 °C, which is also used for pollen, semen, embryos and ova of livestock. Clonally propagated crops (potato, banana, cassava, fruit trees) are kept in field gene banks and in vitro slow-growth cultures. Major facilities include national gene banks such as India's National Bureau of Plant Genetic Resources (New Delhi), the CGIAR centres' collections, and the Svalbard Global Seed Vault in Norway (opened 2008), a back-up facility storing duplicate samples from gene banks worldwide at about −18 °C in permafrost. Animal genetic resources are conserved by national bureaux such as India's National Bureau of Animal Genetic Resources.
Gene bank management involves acquisition and collecting with prior informed consent, characterisation and evaluation, documentation, regular viability testing and regeneration when viability falls (commonly below 85 % of initial viability), safety duplication, and distribution to users under standard agreements (see environmental-law-policy for the plant treaty). Core collections — subsets capturing most of the diversity of a large collection — make evaluation manageable. Risks include loss of viability, genetic drift during regeneration, inadequate funding, civil conflict (the ICARDA gene bank in Aleppo had to rebuild its collections from Svalbard duplicates) and the gap between conserved material and its use by farmers and breeders. Linking ex-situ conservation with on-farm conservation of landraces by farmers and community seed banks keeps varieties evolving under real conditions and supports farmers' rights.
An alien (non-native) species is one introduced outside its natural range by human action; an invasive alien species is one whose introduction and spread threaten biodiversity, and often also economies and human health. Introductions are intentional (crops, ornamentals, pets, aquaculture, biological control, forestry) or unintentional (contaminants of seed and grain, hitchhikers on ships and containers, ballast water, horticultural soil). The invasion process passes through stages — transport, introduction, establishment and spread (Blackburn and colleagues' unified framework) — with barriers at each stage that most species fail to cross. Williamson's 'tens rule' suggests that roughly one in ten imported species appears in the wild, one in ten of those becomes established and one in ten of those becomes a pest; so of 1000 imported species, about one becomes a pest. Traits associated with invasiveness include rapid growth and reproduction, broad tolerance and escape from natural enemies in the new range (the enemy release hypothesis).
The IPBES assessment of invasive alien species (2023) reported more than 37000 established alien species worldwide, found that invasive alien species were a major factor in about 60 % of recorded global plant and animal extinctions, and estimated their global economic costs at more than 423 billion US dollars a year in 2019, quadrupling every decade since 1970. Island ecosystems are particularly vulnerable: the brown tree snake eliminated most native forest birds on Guam, and introduced rats, cats and goats have caused many island extinctions. In India, major invasive plants include lantana (Lantana camara), which has spread through large areas of forest and pasture, mesquite (Prosopis juliflora) in drylands and grasslands, parthenium (Parthenium hysterophorus), a weed of croplands that causes allergies and dermatitis, water hyacinth (Eichhornia crassipes) clogging water bodies, and Mikania micrantha in the north-east and Western Ghats. Elsewhere, the Nile perch transformed Lake Victoria's fish fauna, and the cane toad spread across northern Australia. Invasive pests and pathogens of crops — such as the fall armyworm, which spread from the Americas to Africa (2016) and Asia, including India (2018) — are a direct threat to agriculture.
Management follows a hierarchy. Prevention is the most cost-effective: border biosecurity, quarantine and phytosanitary measures under the International Plant Protection Convention, ballast water management under the International Maritime Organization convention, risk assessment of intentional introductions, and pathway management. Early detection and rapid response deal with new incursions while populations are small, when eradication is feasible. Eradication — complete removal — has succeeded on many islands for rats and goats. Where eradication is impossible, containment limits spread, and long-term control reduces abundance and impacts by mechanical, chemical or biological means. Classical biological control introduces host-specific natural enemies from the invader's native range after careful testing: examples include the Mexican beetle Zygogramma bicolorata against parthenium and Neochetina weevils against water hyacinth in India. Restoration of native vegetation after removal and engagement of communities (for example using lantana for furniture and crafts) improve outcomes. The Kunming-Montreal framework's target 6 aims to reduce rates of introduction and establishment of invasive alien species by at least 50 % by 2030 and to eradicate or control them on priority sites such as islands; the EU regulates a list of invasive species of Union concern.
The Convention on Biological Diversity (1992) and its Cartagena and Nagoya Protocols, and the Kunming-Montreal Global Biodiversity Framework (2022), are described in detail in environmental-law-policy; this chapter focuses on how they shape conservation practice. The framework has four goals for 2050 — (A) maintaining and restoring ecosystem integrity, halting human-induced extinction and maintaining genetic diversity; (B) sustainable use of biodiversity and maintenance of nature's contributions to people; (C) fair and equitable sharing of benefits from genetic resources and digital sequence information; and (D) adequate means of implementation, including finance — and 23 targets for 2030, among them spatial planning to bring the loss of high-importance areas close to zero (target 1), restoring 30 % of degraded ecosystems (target 2), conserving 30 % of land and sea (target 3), halting extinction and recovering species (target 4), sustainable and legal wildlife use (target 5), cutting invasive species (target 6), halving pesticide risk and excess nutrients (target 7), sustainable agriculture, aquaculture, fisheries and forestry (target 10), business disclosure (target 15) and mobilising 200 billion US dollars a year from all sources (target 19). Parties report through updated national biodiversity strategies and action plans (NBSAPs) and national reports using a monitoring framework of headline indicators; India submitted an updated NBSAP with national targets aligned to the framework in 2024.
Access and benefit-sharing (ABS) responds to concerns about 'biopiracy' — the use of genetic resources and associated traditional knowledge without consent or benefit sharing. Under the CBD and the Nagoya Protocol, users need prior informed consent of the provider country and mutually agreed terms on benefits, which can be monetary (fees, royalties, milestone payments) or non-monetary (research collaboration, technology transfer, training). India's Biological Diversity Act 2002, amended in 2023, regulates access: foreign persons and entities need approval of the National Biodiversity Authority to obtain biological resources or associated knowledge, Indian entities must give prior intimation to State Biodiversity Boards for commercial use, and benefit-sharing is negotiated with benefit claimers; the 2023 amendment exempted cultivated medicinal plants and codified traditional knowledge in some cases and decriminalised offences. A frequently cited benefit-sharing example is the arrangement in the 1990s under which a Kerala research institute licensed a herbal formulation based on Trichopus zeylanicus (arogyapacha), known from the Kani tribe, and shared licence fees and royalties with the community through a trust. India challenged patents on the wound-healing use of turmeric (revoked by the United States patent office in 1997) and on a neem-based fungicide (revoked in Europe), and created the Traditional Knowledge Digital Library (2001) to document prior art and prevent such patents.
National biodiversity law combines several layers: species protection (India's Wildlife (Protection) Act schedules, the US Endangered Species Act), area protection (protected areas, eco-sensitive zones, Natura 2000 sites in the EU), habitat and land-use regulation (forest laws, environmental impact assessment, wetland rules), trade regulation (CITES implementation), biosafety (genetic modification approvals under Cartagena-based rules) and access and benefit-sharing. Effectiveness depends on enforcement capacity, integration with agriculture, forestry, fisheries and infrastructure policies, adequate finance, and the participation and rights of indigenous peoples and local communities, whose territories hold a large share of remaining biodiversity. For practitioners in agriculture, the practical questions are which species and habitats on or near a site are legally protected, whether an activity needs clearance, how genetic resources and traditional knowledge may be accessed and shared, and how farm and landscape management can contribute to national targets, for example through OECMs, agroforestry and pollinator habitat (see ecosystem-services-pollinators).
A student must define biodiversity at its three levels, compute Shannon, Simpson, evenness, Jaccard, Sørensen and beta diversity, apply the species-area relationship and island biogeography, calculate effective population size, inbreeding and heterozygosity loss, classify species using IUCN criteria thresholds, name hotspots and India's biogeographic zones, explain in-situ and ex-situ methods with examples, describe invasive species management with Indian examples, and outline the GBF and ABS. These topics are heavily examined in ICAR, GATE and UPSC papers, often as short numerical or matching questions, so regular practice with real data sets is essential.
A biodiversity officer, ecologist or conservation manager designs and runs surveys, analyses diversity data, prepares biodiversity sections of EIAs and corporate disclosures, applies Red List and legal status to project sites, plans habitat management and restoration, manages invasive species, and works with communities on protected areas and benefit sharing. In agriculture and agribusiness, they map biodiversity on farms and supply chains, advise on field margins, wetlands and set-aside, and translate national targets into site action. They must defend survey results to clients and regulators, and know when a site's species or habitats make a proposal unacceptable rather than mitigable.
A protected-area director, head of biodiversity at a company or NGO, or government official sets conservation priorities and budgets, designs protected area and OECM networks, negotiates with communities and other sectors, oversees species recovery and invasive species programmes, and represents the country or organisation in CBD processes. They balance conservation with livelihoods and development, and decide where limited funds achieve most. They must also manage human–wildlife conflict, secure long-term finance, and judge when to accept trade-offs with development and when to refuse them, explaining those choices to the public.
A professor or principal scientist researches biodiversity patterns and change, extinction risk modelling, population genetics of threatened species, effectiveness of protected areas and OECMs, invasion biology, restoration ecology and the integration of biodiversity into agricultural landscapes. They contribute to IPBES and Red List assessments, design monitoring with eDNA and remote sensing, advise on NBSAPs and legislation, supervise doctoral students and set examination questions that test ecological reasoning rather than lists of names. They also train the next generation of field ecologists.
Counts of protected areas, biosphere reserves, hotspots, Ramsar sites, threatened species and India's PA network change frequently and are given approximately with source years. Detailed treaty provisions are in environmental-law-policy, and field methods and protected area management in the forestry subjects forest-ecology, wildlife-biology-ecology and wildlife-management-protected-areas. The manual does not cover marine biodiversity and fisheries management in depth, microbial diversity, phylogenetics and molecular methods beyond outline, or the details of species recovery programmes. Valuation methods are left to natural-resource-environmental-economics.
Original practice questions written to the syllabus and pattern of the exams named in each question's examTags. They are not past papers and do not reproduce any board's questions. Every numerical answer was computed in a script. Counts and percentages are quoted from the cited assessments and change as they are updated.
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