6 Biodiversity and Conservation
Learn how biodiversity is organized and measured, why it matters, what threatens it, and how conservation can protect and restore life on Earth.
The three levels of
is the variety of life and its ecological relationships. It is understood at three connected levels:
: differences in inherited traits among individuals and populations of a species. This variation can help populations adapt when conditions change.
Species diversity: the variety of species in an area and how abundant each species is.
Ecosystem diversity: the variety of habitats, biological communities, and ecological processes across a landscape or region.
A forest, for example, includes genetic differences among its trees, many species of plants and animals, and a range of habitats such as woodland, streams, and wetlands. These levels connect: species depend on habitats, and variation within species can affect how populations respond to changing conditions.
Takeaway: describes variation within species, among species, and across ecosystems.
Measuring
Species diversity has two useful components. is the number of species in a defined area, while describes how equally individuals are distributed among those species.
A meadow with four species represented by similar numbers of individuals has greater than a meadow where almost all individuals belong to one species. The two meadows may have the same richness, but their species are distributed differently. Ecologists may combine richness and in a diversity index.
is measured at different scales, so no single number captures every aspect of it. Scientists may also assess genetic variation within populations, the extent and condition of ecosystems, changes in species abundance, and extinction risk. The IUCN Red List classifies species’ risk of global extinction using defined criteria; it is one indicator, not a complete measure of . Comparisons are most meaningful when sampling area, methods, and effort are similar.
Takeaway: Interpret measures in context: richness, , genetic variation, habitat condition, and extinction risk describe different aspects.
Why matters
Living things interact through food webs, pollination, decomposition, and nutrient cycling. These ecological processes help ecosystems provide benefits people rely on, including food, clean water, fertile soils, pollination, climate regulation, and cultural and recreational values.
also has intrinsic value, and conserving it preserves options for future generations. A range of species and genetic traits can help some ecosystems continue functioning as conditions change. However, diversity alone does not guarantee stability or resilience. These also depend on which organisms are present, the roles they play, habitat condition, and the disturbances an ecosystem faces.
Takeaway: supports ecological processes and human well-being, but ecosystem resilience depends on more than diversity alone.
Major threats to
Five major direct pressures drive decline:
Land- and sea-use change: converting or fragmenting habitats, such as clearing forest for roads or agriculture.
Direct exploitation: unsustainable hunting, fishing, logging, or collection.
Climate change: shifts in temperature, rainfall, ocean conditions, and disturbance patterns.
Pollution: contaminants, excess nutrients, plastics, and other pollutants that harm organisms or alter habitats.
: introduced species that spread beyond their natural range and cause harm to native species or ecosystems.
These pressures can interact. For example, habitat fragmentation can make it harder for a species to move as climate conditions change. This means that addressing one pressure may also help reduce the effects of another.
Takeaway: decline is driven by multiple pressures that can compound one another.
in practice
combines approaches suited to particular species, ecosystems, and communities:
Protect habitats in place. Protected areas and other effective measures can safeguard habitats, populations, and ecological connections. Success depends on fair and effective management, not simply designation on a map.
Restore degraded ecosystems. Restoration can help recover native species, ecological functions, and connections between habitats. It should fit the ecosystem and local context; planting trees alone does not necessarily restore a natural forest.
Use biological resources sustainably. Science-based limits and responsible farming, forestry, and fishing practices can reduce pressure while allowing resources to be used over time.
Reduce specific threats. Actions can include reconnecting habitats, controlling invasive species, reducing pollution, and limiting illegal or excessive exploitation.
Conserve species and genetic resources. Seed banks, botanical gardens, and captive breeding can support recovery, but do not replace functioning habitat.
Include local and Indigenous communities. Durable and equitable planning respects the rights and knowledge of people who live in and steward the places being conserved.
Monitor and adapt. Repeated surveys help determine whether populations and habitats are improving and whether actions need to change.
The Kunming–Montreal Global Framework calls for effective restoration of at least 30% of degraded terrestrial, inland-water, coastal, and marine ecosystems by 2030. This is a global target; meaningful recovery depends on appropriate and effective action in each place.
Takeaway: Effective protects and restores habitats, reduces pressures, involves affected communities, and adapts in response to monitoring.