Module 8: Conservation & the Anthropocene

Norman Myers proposed the biodiversity-hotspot concept in 1988 and crystallised it with Mittermeier, Mittermeier, da Fonseca and Kent in Myers et al. (2000 Nature 403, 853–858). A region qualifies as a hotspot if it meets two strict criteria:

• Endemism: > 1500 endemic vascular plant species.
• Threat: > 70% of original habitat already lost.

Myers identified 25 hotspots in 2000; Conservation International and Mittermeier have expanded the list to 36 as of 2023. Together they cover only ~16% of the terrestrial surface but contain roughly 43% of all endemic vertebrate species and 44% of all endemic plants. The concept transformed global conservation funding by providing a defensible quantitative prioritisation: limited dollars should flow to regions where the most irreplaceable biodiversity is at greatest risk.

Canonical hotspots include:

• Mediterranean Basin: 22,500 endemic plants (out of 25,000 total); high ancient human impact; classic Mediterranean-type climate (Module 5).
• Madagascar & Indian Ocean Islands: extraordinary endemic fauna (lemurs, chameleons, mantellid frogs) after > 80 Myr of isolation.
• Sundaland: the lowland rainforest of Borneo, Sumatra, peninsular Malaysia; orangutan, Sumatran rhinoceros, Javan rhinoceros, staggering arthropod diversity.
• Atlantic Forest (Mata Atlântica): ~8% of original extent remaining; endemic primates, antbirds, bromeliad-epiphyte radiations.
• Tropical Andes: the single most biodiverse hotspot on Earth — 30,000+ plant species, 1700+ bird species.
• Caribbean islands: classic island biogeography; high endemism on each island group (Hispaniola endemic solenodons, Cuban tody, Caribbean insular bats).

The Myers framework was operationalised by Conservation International, the IUCN Red List (Mace et al. 2008), and various national prioritisation schemes. Kareiva & Marvier (2003 American Scientist) argued for an expanded “hotspots with cold-spots” strategy: protect hotspots for irreplaceability, but also protect wilderness “cold spots” (Amazon, boreal forest) because of sheer size and functional importance for climate regulation.

The SLOSS debate — Single Large Or Several Small reserves — dominated early conservation biology (Simberloff & Abele 1976, 1982 American Naturalist) and remains unresolved because the answer is context-dependent. For species-area curves of slope \(z \approx 0.25\)(Module 2), a single reserve of area \(A\) holds more species than two reserves of \(A/2\) each only if the two reserves share most of their species. If the reserves are in different biomes or on different sides of a biogeographic barrier, SS outperforms SL.

Modern reserve design therefore emphasises landscape-level networks: individual reserves connected by corridors that permit genetic and demographic exchange. Beier & Noss (1998 Conservation Biology) reviewed the empirical corridor literature and concluded that well-designed corridors do function — documented gene flow, pollination and seed dispersal through connecting habitat. Gilbert-Norton et al. (2010 Conservation Biology) meta-analysed 33 studies and found corridors raised movement rates by 50% on average.

Design principles (Diamond 1975 Biological Conservation; MacArthur–Wilson-derived):

• One large reserve beats many small (given similar species).
• Round shape beats elongated (minimise edge effects).
• Connected beats isolated (corridors or stepping stones).
• Close clusters beat distant clusters.
• Buffer zones dampen edge effects.

Margules & Pressey (2000 Nature 405, 243–253) formalised systematic conservation planning as a six-step iterative optimisation: (1) compile data, (2) set quantitative targets, (3) review existing reserves, (4) select additional areas, (5) implement, (6) monitor. The mathematical core is a constrained-minimisation problem, usually set-cover or maximal-coverage variants, which are NP-hard.

MarxAN (Ball, Possingham & Watts 2009) uses simulated annealing to optimise this objective. Zonation (Moilanen et al. 2009 Bioinformatics) takes an alternative approach — iteratively removing the least-valuable planning units in reverse order, producing a ranked landscape-priority surface rather than a single solution. Prioritizr (Hanson et al. 2018) provides a modern R package using mixed-integer linear programming solvers (Gurobi) that can find provably-optimal solutions for moderately-sized problems where MarxAN only finds heuristic solutions.

These tools now underpin national and continental conservation plans: Australia’s National Reserve System, the European Natura 2000 network, and the marine spatial plans of California, Canada and the Great Barrier Reef Marine Park. The 30×30 goal (CBD Kunming-Montreal Global Biodiversity Framework 2022, Target 3) of protecting 30% of terrestrial and marine areas by 2030 is a systematic-planning problem at the planetary scale.

As climate warms and ranges shift poleward and upslope (Module 5), static reserves designed for present-day species distributions will progressively fail. Ackerly et al. (2020 Annual Review of Ecology, Evolution, and Systematics) formalised the concept of climate-adjacent lands: areas outside existing reserves that will become the future analogue climate for species currently in-reserve, and that must be protected now to permit range-shift tracking.

Where climate velocity exceeds dispersal capacity — common for long-lived trees, flightless invertebrates, and mountain-endemic taxa with no upslope habitat — passive range-shift tracking will not suffice. Assisted colonisation (also “managed relocation”; McLachlan, Hellmann & Schwartz 2007 Conservation Biology; Hoegh-Guldberg et al. 2008 Science) proposes deliberate human-mediated translocation of species ahead of climate change to refugia they cannot reach unaided.

Assisted colonisation is ethically and ecologically fraught. Risks include introduction shock, invasion of recipient communities, disease transfer, and loss of local-adaptation genetic architecture. Early successful cases include Bay Checkerspot butterfly (Euphydryas editha bayensis) reintroductions to climate-appropriate sites, and the Australian western swamp turtle (Pseudemydura umbrina) to cooler southern wetlands. Many practitioners advocate for “assisted migration” within the native range (e.g. shifting seed sources northward within a species’ historical distribution) as a less controversial middle ground.

Human-mediated species introductions are reorganising the global biota. McKinney & Lockwood (1999 TREE) introduced the concept of biotic homogenisation: the process by which regional biotas become increasingly similar through the widespread success of a few cosmopolitan invasive species and the loss of regionally-endemic natives. McKinney (2006 Biological Conservation) showed that for North American urban bird communities, similarity (Jaccard index) had increased by 10–20% over 50 years, confirming homogenisation on a continental scale.

Invasive-species introduction pathways include ballast-water transport (marine invaders), ornamental horticulture (terrestrial plants), fruit and food trade (insect pests), pet trade (reptiles, amphibians), and intentional biocontrol (cane toads in Australia, a famous failure). The most-damaging global invasives — brown rat (Rattus norvegicus), domestic cat, red fox, zebra mussel, water hyacinth, Rhinella marina cane toad, kudzu vine — have together caused hundreds of extinctions and billions in economic damage.

Island biotas are especially vulnerable: Blackburn et al. (2004 Science) showed that ~90% of recorded bird extinctions occurred on islands, and that introduced predators (rats, cats) were the single largest cause. Island eradication programmes (rat eradications on > 700 islands; the New Zealand predator-free-by-2050 programme) are among the most effective conservation tools available.

Environmental DNA (eDNA) refers to genetic material shed by organisms into water, soil, or air, which can be PCR-amplified to detect species presence without trapping, observing, or collecting individuals. Taberlet et al. (2012 Molecular Ecology) reviewed the founding methodology; since then eDNA has become a standard tool for fish surveys (Thomsen et al. 2012 PLoS ONE), invasive-species detection, rare-species confirmation, and whole-community metabarcoding.

eDNA has revolutionised aquatic biodiversity assessment. A single 1-litre water sample can reveal the presence of hundreds of fish, amphibian, or invertebrate species. For marine biodiversity, metabarcoding of seawater replaces labour-intensive trawls. Airborne eDNA (Lynggaard et al. 2022 Current Biology) recently demonstrated vertebrate detection from filter-collected air in temperate Europe and tropical zoos.

Camera-trap networks (Ahumada et al. 2011 Phil. Trans.; TEAM Network) and acoustic biodiversity monitoring (Aide et al. 2013 PeerJ) provide complementary high-throughput methods. Integration of eDNA, acoustics, camera traps, and remote sensing is now enabling automated biodiversity inventories at landscape scales — the technological underpinning of next-generation monitoring that CBD signatories have committed to under the Global Biodiversity Framework.

Geldmann et al. (2019 PNAS) performed the largest meta-analysis of protected-area effectiveness, covering > 3 million km² and showing that protected areas reduce deforestation by ~30% compared to matched controls, though with high regional variation. “Paper parks” — designated but unfunded or unenforced — provide little protection. The best-performing reserves are strictly protected (IUCN categories I–II), well-funded, and have local community support.

Watson et al. (2014 Nature 515, 67–73) argued that performance is more important than coverage: 30% of land in ineffective reserves achieves less than 10% of land in effective reserves. This has shifted the global conservation conversation from coverage targets (17% by 2020 under CBD Aichi Targets) to effectiveness metrics (30×30 by 2030 under the Global Biodiversity Framework). The framework also recognises “other effective area-based conservation measures” (OECMs), such as sacred sites and traditional indigenous territories, which can deliver biodiversity outcomes without formal reserve status.

Indigenous land management is increasingly recognised as a major conservation asset. Garnett et al. (2018 Nature Sustainability) estimated that > 25% of terrestrial land globally is managed or used by indigenous peoples, and biodiversity on indigenous-managed lands is on average no worse, and often better, than on formally protected areas. Partnerships with indigenous communities are now a central pillar of 21st-century conservation.

Rewilding (Fraser 2014 Rewilding the World; Sandom et al. 2013 Proc. Roy. Soc. B) aims to restore ecosystem processes by returning keystone species — particularly large herbivores and apex predators — to landscapes from which they were extirpated. The flagship case is the 1995 reintroduction of gray wolves (Canis lupus) to Yellowstone National Park, which triggered a cascade of effects through elk browsing pressure, willow regeneration, beaver recovery, and stream-channel restoration (Ripple & Beschta 2012 Biological Conservation).

European rewilding projects include the Oostvaardersplassen experiment in the Netherlands (mixed grazer introduction); the Iberian lynx recovery in Spain and Portugal; the Wild Europe and Rewilding Europe networks targeting 1 million km² of rewilded area by 2030. Pleistocene Park in Siberia (Zimov 2005) proposes reconstructing mammoth-steppe ecosystems by introducing extant Holarctic megafauna (bison, yakut horses, musk ox) to trigger grassland-forest state transitions.

Rewilding has also become a framework for marine conservation. The recovery of humpback whale (Megaptera novaeangliae) populations after 1966 whaling moratoria, sea otter recovery on the North Pacific coast (Estes & Palmisano 1974 Science), and Pacific salmon-run restoration are all documented rewilding successes. The ecosystem-services benefits of rewilding, including carbon sequestration and flood control, are increasingly cited in cost-benefit analyses of conservation investment.

Daniel Pauly (1995 TREE 10, 430) coined the term “shifting baselines” for the fisheries-management pattern in which each generation of scientists accepts the depleted stocks of their youth as normal, progressively ratcheting expectations downward. Jackson et al. (2001 Science 293, 629–637) extended this to marine ecosystems broadly, showing that the sea-grass beds, coral reefs, and reef fish populations of today are a shadow of their pre-industrial state, with baseline shifting starting as early as mid-19th-century whaling.

Crutzen & Stoermer (2000) proposed that we have entered the Anthropocene, a new geologic epoch characterised by human dominance of the planetary surface. The Anthropocene Working Group of the International Commission on Stratigraphy voted in 2024 not to formalise the Anthropocene as a chronostratigraphic unit, though the concept remains central to environmental science. Candidate Global Boundary Stratotype markers include artificial radionuclides from atmospheric nuclear testing (Crawford Lake, Ontario, proposed golden spike; Waters et al. 2023 GSA Bulletin), plastic deposition layers, and black-carbon from fossil-fuel combustion.

Waters et al. (2016 Science) documented the multiple sedimentary “Anthropocene markers”: radionuclides from 1952–1963 atmospheric tests; concrete and aluminum as abundant rock types; black-carbon spikes from fossil fuels; fly-ash spherules; novel synthetic minerals and microplastics; nitrogen and phosphorus perturbations from the Haber–Bosch and fertilizer industries; and biostratigraphic markers from agricultural species (chicken bones are now the most numerous vertebrate fossils being deposited globally).

Conservation requires financing. Three decades of market-based instruments have developed alongside traditional protected-area budgets: Payments for Ecosystem Services (PES) programs such as Costa Rica’s landmark 1996 PSA program, which pays private landowners for water-regulation, carbon-storage, and biodiversity services; REDD+ (Reducing Emissions from Deforestation and forest Degradation) carbon markets; and biodiversity offset frameworks tied to corporate impact-mitigation hierarchies.

Wunder (2013 Ecological Economics) reviewed PES effectiveness and concluded that well-designed programmes can reduce deforestation by 10–30% in target landscapes, though leakage (deforestation shifting to adjacent areas) and additionality (paying for what would have happened anyway) remain serious design challenges. Biodiversity-bond financial instruments (e.g. the Rhino Impact Bond launched in 2022) and nature-positive outcome-based investments are the newest wave of conservation finance.

Balmford et al. (2002 Science 297, 950–953) calculated that a global reserve-network expansion would cost ~$45 billion per year and deliver ecosystem services worth $4.4–5.2 trillion per year — a benefit–cost ratio of ~100. Despite this, conservation remains chronically underfunded, with global spending on biodiversity of ~$145 billion per year (Seidl et al. 2021) against needs estimated at $700–850 billion per year to meet Global Biodiversity Framework targets (Deutz et al. 2020 Paulson Institute report).

More than half of humanity now lives in cities. Urban biogeography, formalised by McKinney (2002 BioScience, 2006), treats cities as a distinctive biome with urban heat-island effects, novel substrates (concrete, asphalt), anthropogenic light and sound regimes, and high connectivity to non-native species pools. Urban bird and plant communities show consistent global patterns: 80% of a city’s plant flora is non-native; <20% of native vertebrate species persist in urban cores; and global species similarity between cities exceeds that of their surrounding regions (biotic homogenisation).

Yet cities also harbour surprising biodiversity, especially in peri-urban green-space mosaics and restored brownfields. Some species are urban specialists (rock pigeon, peregrine falcon nesting on skyscrapers, Ailanthus altissima tree-of-heaven). Urban ecological restoration, native-landscaping programs, and urban-stream rewilding are increasingly recognised as conservation strategies in their own right. The Singapore City in a Garden framework, the New York High Line, and the Seoul Cheonggyecheon stream restoration are exemplars.

The Kunming-Montreal Global Biodiversity Framework adopted at CBD COP15 in December 2022 set four long-term goals and twenty-three action targets for 2030. The headline target — Target 3 — is to conserve at least 30% of terrestrial, inland-water, coastal, and marine areas by 2030, with “effectively conserved and managed” language and explicit recognition of Indigenous and local community rights. Implementation is entering a crucial phase: as of 2024, terrestrial coverage sits near 17.6% and marine coverage near 8.3% (Protected Planet database).

Meeting 30×30 will require not just adding area but redistributing protection spatially: more coverage of currently under-represented ecoregions (freshwater, temperate grasslands, tropical dry forests); more marine protection outside national jurisdiction (pending the High Seas Treaty ratification); and more climate-adjacent and climate-refugia protection. Systematic-planning tools (Module Section 3) are essential for targeting expansions effectively.

Beyond 30×30, the emerging conversation is about nature-positive futures: not merely halting biodiversity loss but actively reversing it by 2030–2050. This requires integrating conservation biogeography with climate policy, food-system transformation, and the reduction of the ~75–80% of the planet’s surface that is currently used for agriculture, grazing, or human settlement. Biogeography — from Humboldt’s first-generation descriptions through MacArthur–Wilson’s equilibrium theory to today’s genomic and remote-sensing tools — is now the scientific backbone of the planetary stewardship agenda.