APES 2.1-2.2: Introduction to Biodiversity and Ecosystem Services

Biodiversity

The variability of life on Earth, including variation within species, among species, and among ecosystems. It can also include functional and phylogenetic differences.

What are the major levels at which biodiversity can be measured?

Important levels include genetic diversity within species, species diversity, ecosystem diversity, and phylogenetic diversity. Functional and morphological diversity are also used in some contexts.

Genetic diversity

The variation in genes and alleles among individuals within a species or population. Greater genetic diversity can increase a population's ability to adapt to environmental change.

Species richness versus species diversity

Species richness is the number of species in a region, whereas species diversity considers both the number of species and their relative abundances. Thus, two communities can have equal richness but different diversity.

Ecosystem diversity

The variety of ecosystems, habitats, and ecological processes found in a region. It reflects differences such as forests, wetlands, grasslands, and marine ecosystems.

Habitat diversity

The variety of physical environments within a region, such as forests, wetlands, grasslands, deserts, coral reefs, and estuaries. Greater habitat diversity can support more species and ecological niches.

Functional diversity

The variety of ecological roles or traits represented in a community, such as different feeding mechanisms, modes of movement, or predator-prey roles.

Phylogenetic diversity

A measure of the evolutionary relationships represented by organisms in a community. A community containing species from distantly related lineages has greater phylogenetic diversity than one containing closely related species only.

What is the species-area relationship?

It is the ecological pattern that larger areas generally contain more species than smaller areas. It is commonly represented as $S = cA^z$, where $S$ is species richness, $A$ is area, and $c$ and $z$ are empirically determined constants.

How does habitat destruction affect biodiversity through the species-area relationship?

Reducing habitat area generally reduces the number of species that can be supported. Fragmentation can further isolate populations and increase extinction risk, especially for species with small geographic ranges.

Latitudinal gradient in species diversity

The general pattern in which species diversity increases from the poles toward the tropics. The pattern is strong in many terrestrial groups but is not universal across all aquatic organisms or ecological groups.

Why is biodiversity generally greater in tropical regions than near the poles?

Tropical regions generally have higher temperatures, precipitation, and primary productivity, which can support more species and ecological niches. Biodiversity is therefore often described as increasing toward the equator.

Primary productivity

The rate at which producers convert energy, usually light energy, into chemical energy stored in organic matter. High primary productivity can provide more energy to support diverse food webs.

How do tropical forests contribute disproportionately to global biodiversity?

They occupy less than one-fifth of Earth's terrestrial area yet contain approximately half of the world's species. Their warm, wet climates and high productivity create many suitable habitats and niches.

Biodiversity hotspot

A region with unusually high numbers of endemic species that has also experienced substantial habitat loss. Hotspots are often tropical forest regions or other areas with specialized habitats.

Endemic species

A species that occurs naturally in a particular geographic region and nowhere else. Islands and isolated habitats often have many endemic species because populations evolve independently.

Why can isolated islands have unusually high endemism?

Geographic isolation limits gene flow with mainland populations. Over time, isolated populations can evolve independently, producing species found nowhere else.

Mass extinction

A geologically brief interval during which biodiversity decreases sharply across many unrelated groups. Earth's history includes several major mass extinctions and smaller extinction events.

Holocene extinction or sixth mass extinction

The ongoing, human-driven acceleration of species and population losses in the recent geological period. Major causes include habitat destruction, overexploitation, pollution, and climate change.

What is the primary direct cause of current biodiversity loss?

Human-driven habitat destruction, especially conversion of natural ecosystems for agriculture, is identified as a major cause. Overexploitation of wildlife and climate change are also important drivers.

How can climate change reduce biodiversity?

Climate change alters temperature, precipitation, biome boundaries, and other conditions on which organisms depend. Species unable to migrate, acclimate, or adapt may experience population declines or extinction.

Ecological resilience

The capacity of an ecosystem or population to withstand disturbance and recover while retaining its functions. Loss of biodiversity can reduce resilience and adaptability.

Why is biodiversity important to ecosystem functioning?

Biodiversity supports complex food webs, nutrient cycling, productivity, pollination, decomposition, and other ecological processes. Greater diversity can also increase ecosystem stability and resilience.

Ecosystem services

Benefits that ecosystems provide to humans. They include provisioning, regulating, cultural, and supporting services.

Provisioning ecosystem services

Material benefits obtained from ecosystems, including food, freshwater, fuel, timber, fibers, medicines, and genetic resources.

Regulating ecosystem services

Benefits produced by ecosystem processes that regulate environmental conditions, including climate regulation, water purification, flood control, erosion control, pollination, and pest regulation.

Cultural ecosystem services

Nonmaterial benefits people obtain from ecosystems, including recreation, tourism, aesthetic enjoyment, spiritual and cultural value, education, and inspiration.

Supporting ecosystem services

Underlying ecosystem processes that enable other services, including primary production, soil formation, nutrient cycling, decomposition, and habitat provision.

How can biodiversity support human food systems?

Different species provide food directly and support pollination, soil processes, pest control, and genetic resources for agriculture. Greater biological variety can make food systems more resilient to pests and environmental change.

Why is genetic diversity important in agriculture?

Genetic variation provides traits that may confer resistance to diseases, pests, drought, or changing temperatures. Maintaining diverse crop varieties can therefore improve long-term food security.

How can biodiversity affect human health?

Biodiversity supports ecosystem services such as clean water, food production, and climate regulation. It also provides biological resources that can contribute to medicines and other health-related products.

Why are biodiversity and climate regulation interconnected?

Biodiverse ecosystems can improve climate mitigation and adaptation by storing carbon and maintaining ecological functions. Climate change, in turn, can damage ecosystems and reduce biodiversity.