Biodiversity

Biodiversity is defined as “the variability among living organisms from all sources including air, 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.”

Biodiversity includes all ecosystems—managed or unmanaged.

Unmanaged ecosystems include wildlands, nature preserves, or national parks and managed systems are planta­tions, farms, croplands, aquaculture sites, rangelands, or even urban parks and urban ecosystems. Each have their own biodiversity.

An effective understanding of biodiversity and how it is changing over space and time, is needed. The factors responsible for such change, the consequences of such change for ecosystem services and human well-being, and the management options available are important

Documenting Biodiversity

The abundance of all organisms over space and time is done by using (1) taxonomy (such as the number of species) (2) functional traits (for example, the ecological type such as nitrogen-fixing plants like legumes versus non-nitrogen-fixing plants) (3)  interactions among species that affect their dynamics and function (predation, parasitism, compe­tition and activities such as pollination, for instance, and how strongly such interactions affect ecosystems).

Measures of Biodiversity

There are many measures of biodiversity-

Species richness (the number of species in a given area) represents one of the important metric of the diversity of life. These include the species richness of specific taxa, the number of distinct plant functional types (such as grasses, forbs, bushes, or trees), or the diversity of distinct gene sequences in a sample of microbial DNA taken from the soil. However, such species- or other taxon-based measures of biodiversity, rarely capture key attributes such as variability, function, quantity, and distribution. All these provide insight into the roles of biodiversity.

Ecological indicators are scientific concepts that use quantitative data to measure aspects of biodiversity, ecosystem condition, services, or factors of change. No single ecological indicator captures all the dimensions of biodiversity. Some environmental indicators, such as global mean temperature and atmospheric CO2 concentrations, are becoming widely accepted as measures of anthropogenic effects on global climate. Ecological indicators help in monitoring, assessing and decision-making. Their presence or absence help in understanding and communicating information quickly and easily to public and policy-makers.

Significance of Biodiversity

Biodiversity is essentially everywhere, ubiquitous on Earth’s surface and in every drop of its bodies of water. The omnipresence of life on Earth is not much appreciated because most organisms are small, their presence is sparse, short-lived, or hidden, or, in the case of microbes, invisible to the unaided human eye.

 Biodiversity plays an important role in ecosystem functions that provide supporting, provisioning, regulating, and cultural services. These services are essential for human well-being. However, at present there are few studies that link changes in biodiversity with changes in ecosystem functioning to changes in human well-being. Further work that demonstrates the links between biodiversity, regulating and supporting services, and human well-being is needed to show this vital and unappreciated value of biodiversity.

Species composition is more important than species richness when it comes to ecosystem functioning. Ecosystem functioning at any given moment in time is strongly influenced by the ecological characteristics of the most abundant species, not by the number of species. The relative importance of a species to ecosystem functioning is determined by its traits and its relative abundance. For example, the traits of the dominant or most abundant plant species—such as how long they live, how big they are, how fast they assimilate carbon and nutrients, how decomposable their leaves are, or how dense their wood is—are usually the key species drivers of an ecosystem’s processing of matter and energy. Thus conserving or restoring the composition of biological communities, rather than simply maximizing species numbers, is critical to maintaining ecosystem services.

Local or functional extinction, or the reduction of populations to the point that they no longer contribute to ecosystem functioning, can have dramatic impacts on ecosystem services. Local extinctions (the loss of a species from a local area) and functional extinctions (the reduction of a species such that it no longer plays a significant role in ecosystem function) have received little attention compared with global extinctions (loss of all individuals of a species from its entire range). Loss of ecosystem functions, and the services derived from them, occurs long before global extinction.

When the functioning of a local ecosystem has been pushed beyond a certain limit by direct or indirect biodiversity alterations, the ecosystem-service losses persist for a very long time.

Changes in biotic interactions among species—predation, parasitism, competition, and facilitation—can lead to disproportionately large, irreversible, and often negative alterations of ecosystem processes. In addition to direct interactions, such as predation, parasitism, or facilitation, the maintenance of ecosystem processes depends on indirect interactions as well, such as a predator preying on a dominant competitor such that the dominant is suppressed, which allows subordinate species to coexist. Interactions with important consequences for ecosystem services include pollination; links between plants and soil communities, including mycorrhizal fungi and nitrogen-fixing microorganisms; links between plants and herbivores and seed dispersers; interactions involving organisms that modify habitat conditions (beavers that build ponds, for instance, or tussock grasses that increase fire frequency); and indirect interactions involving more than two species (such as top predators, parasites, or pathogens that control herbivores and thus avoid overgrazing of plants or algal communities) 

Many changes in ecosystem are brought about by the removal or introduction of organisms in ecosystems that disrupt biotic interactions. Because the network of interactions among species and the network of linkages among ecosystem processes are complex, the impacts of either the removal of existing species or the introduction of new species are complex and difficult to predict.

As in terrestrial and aquatic communities, the loss of individual species involved in key interactions in marine ecosystems can also influence. For example, coral reefs and their role ecosystem services they provide are directly dependent on the maintenance of some key interactions between animals and algae. As one of the most species-rich communities on Earth, coral reefs are responsible for maintaining a vast storehouse of genetic and biological diversity. Coral reefs are habitats to aquatic life and have a role in nutrient cycling and carbon and nitrogen fixing in nutrient-poor environments; and wave buffering and sediment stabilization. The total economic value of reefs and associated services is estimated as hundreds of millions of dollars. Yet all coral reefs are dependent on a single key biotic interaction: symbiosis with algae. The dramatic effects of climate change and variability (such as El Niño oscillations) on coral reefs are medi­ated by the disruption of this symbiosis.

More reading

https://www.greenfacts.org/en/biodiversity/l-3/1-define-biodiversity.htm