Biodiversity is defined as “the variability among living organisms from all sources including, inter alia, terrestrial, marine and other aquatic ecosystems and the. 'Biological diversity' means the variability among living organisms from all sources including, inter alia, terrestrial, marine and other aquatic ecosystems and the. Definitions.
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More than Species Richness. Ecological Indicators and Biodiversity. Criteria for Effective Ecological Indicators. Biodiversity Synthesis , Chapter 1, p. Documenting spatial patterns in biodiversity is difficult because taxonomic, functional, trophic, genetic, and other dimensions of biodiversity have been relatively poorly quantified.
Even knowledge of taxonomic diversity , the best known dimension of biodiversity, is incomplete and strongly biased toward the species level, megafauna, temperate systems, and components used by people. For these reasons, estimates of the total number of species on Earth range from 5 million to 30 million.
Irrespective of actual global species richness, however, it is clear that the 1. More-complete biotic inventories are badly needed to correct for this deficiency C4. Spatial Patterns of Biodiversity: While the data to hand are often insufficient to provide accurate pictures of the extent and distribution of all components of biodiversity , there are, nevertheless, many patterns and tools that decision-makers can use to derive useful approximations for both terrestrial and marine ecosystems.
North-temperate regions often have usable data on spatial distributions of many taxa, and some groups such as birds, mammals, reptiles, plants, butterflies, and dragonflies are reasonably well documented globally. Biogeographic principles such as gradients in species richness associated with latitude, temperature, salinity, and water depth or the use of indicators can supplement available biotic inventories. Global and sub-global maps of species richness, several of which are provided in the MA reports Current State and Trends and Scenarios , provide valuable pictures of the distribution of biodiversity C4 , S Most macroscopic organisms have small, often clustered geographical ranges, leading to centers of both high diversity and endemism, frequently concentrated in isolated or topographically variable regions islands, mountains, peninsulas.
Even among the larger and more mobile species, such as terrestrial vertebrates, more than one third of all species have ranges of less than 1, square kilometers. In contrast, local and regional diversity of microorganisms tends to be more similar to large-scale and global diversity because of their large population size, greater dispersal, larger range sizes, and lower levels of regional species clustering C4.
Biomes and biogeographic realms provide broad pictures of the distribution of functional diversity. Functional diversity the variety of different ecological functions in a community independent of its taxonomic diversity shows patterns of associations biota typical of wetlands, forests, grasslands, estuaries, and so forth with geography and climate known as biomes see Figure 1.
These can be used to provide first-order approximations of both expected functional diversity as well as possible changes in the distribution of these associations should environmental conditions change. Temporal Patterns of Biodiversity: Background Rates of Extinction and Biodiversity Loss. Knowledge of patterns of biodiversity over time allow for only very approximate estimates of background rates of extinction or of how fast species have become extinct over geological time.
Except for the last 1, years, global biodiversity has been relatively constant over most of human history, but the history of life is characterized by considerable change. The estimated magnitude of background rates of extinction is roughly 0. Current rates of extinction are discussed in Key Question 3. A mismatch exists between the dynamics of changes in natural systems and human responses to those changes.
This mismatch arises from the lags in ecological responses, the complex feedbacks between socioeconomic and ecological systems, and the difficulty of predicting thresholds. Multiple impacts especially the addition of climate change to the mix of forcing functions can cause thresholds, or rapid and dramatic changes in ecosystem function even though the increase in environmental stress has been small and constant over time.
Understanding such thresholds requires having long-term records, but such records are usually lacking or monitoring has been too infrequent, of the wrong periodicity, or too localized to provide the necessary data to analyze and predict threshold behavior C28 , S3.
Shifts to different regimes may cause rapid substantial changes in biodiversity , ecosystem services , and human well-being. Regime shifts have been commonly documented in pelagic systems due to thresholds related to temperature regimes and overexploitation C Some regime shifts are essentially irreversible, such as coral reef ecosystems that undergo sudden shifts from coral-dominated to algal-dominated reefs C The trigger for such phase shifts usually includes increased nutrient inputs leading to eutrophic conditions and removal of herbivorous fishes that maintain the balance between corals and algae.
Once the thresholds both an upper and a lower threshold for the two ecological processes of nutrient loading and herbivory are passed, the phase shift occurs quickly within months , and the resulting ecosystem—though stable—is less productive and less diverse. Consequently, human well-being is affected not only by reductions in food supply and decreased income from reef-related industries diving and snorkeling, aquarium fish collecting, and so on , but also by increased costs due to diminished ability of reefs to protect shorelines.
Algal reefs are more prone to being broken up in storm events, leading to shoreline erosion and seawater breaches of land C Introduced invasive species can act as a trigger for dramatic changes in ecosystem structure, function, and delivery of services.
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. Protecting the Catskill watersheds that provide drinking water for New York City is one case where safeguarding ecosystem services paid a dividend of several billion dollars.
Further work that demonstrates the links between biodiversity, regulating and supporting services , and human well-being is needed to show this vital but often unappreciated value of biodiversity C4, C7, C Species composition matters as much or more than species richness when it comes to ecosystem services.
Ecosystem functioning, and hence ecosystem services, 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. Thus conserving or restoring the composition of biological communities , rather than simply maximizing species numbers, is critical to maintaining ecosystem services C 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, however, occurs long before global extinction.
Often, when the functioning of a local ecosystem has been pushed beyond a certain limit by direct or indirect biodiversity alterations, the ecosystem-service losses may persist for a very long time C 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 permits 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 C Many changes in ecosystem services are brought about by the removal or introduction of organisms in ecosystems that disrupt biotic interactions or ecosystem processes.
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 difficult to anticipate C Ecological Surprises Caused by Complex Interactions.
As in terrestrial and aquatic communities , the loss of individual species involved in key interactions in marine ecosystems can also influence ecosystem processes and the provisioning of ecological services. For example, coral reefs and the 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.
Substantial ecosystem services are provided by coral reefs—such as habitat construction, nurseries, and spawning grounds for fish; 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: Biodiversity affects key ecosystem processes in terrestrial ecosystems such as biomass production , nutrient and water cycling, and soil formation and retention—all of which govern and ensure supporting services high certainty. The relationship between biodiversity and supporting ecosystem services depends on composition, relative abundance, functional diversity , and, to a lesser extent, taxonomic diversity.
If multiple dimensions of biodiversity are driven to very low levels, especially trophic or functional diversity within an ecosystem, both the level and stability for instance, biological insurance of supportive services may decrease CF2 , C Region-to-region differences in ecosystem processes are driven mostly by climate, resource availability, disturbance, and other extrinsic factors and not by differences in species richness high certainty.
In natural ecosystems , the effects of abiotic and land use drivers on ecosystem services are usually more important than changes in species richness. Plant productivity , nutrient retention, and resistance to invasions and diseases sometimes grow with increasing species numbers in experimental ecosystems that have been reduced to low levels of biodiversity. In natural ecosystems, however, these direct effects of increasing species richness are usually overridden by the effects of climate, resource availability, or disturbance regime C Even if losses of biodiversity have small short-term impacts on ecosystem function, such losses may reduce the capacity of ecosystems for adjustment to changing environments that is, ecosystem stability or resilience, resistance, and biological insurance high certainty.
The loss of multiple components of biodiversity, especially functional and ecosystem diversity at the landscape level, will lead to lowered ecosystem stability high certainty. Although the stability of an ecosystem depends to a large extent on the characteristics of the dominant species such as life span, growth rate, or regeneration strategy , less abundant species also contribute to the long-term preservation of ecosystem functioning.
As tragically illustrated by social conflict and humanitarian crisis over droughts, floods, and other ecosystem collapses, stability of ecosystems underpins most components of human well-being , including health , security, satisfactory social relations, and freedom of choice and action C6 ; see also Key Question 2.
The preservation of the number, types, and relative abundance of resident species can enhance invasion resistance in a wide range of natural and semi-natural ecosystems medium certainty. Although areas of high species richness such as biodiversity hot spots are more susceptible to invasion than species- poor areas, within a given habitat the preservation of its natural species pool appears to increase its resistance to invasions by non-native species. This is not because species diversity is more important than the other two types, but because: Species diversity is easier to work with.
Species are relatively easy to identify by eye in the field, whereas genetic diversity see below requires laboratories, time and resources to identify, and ecosystem diversity see below needs many complex measurements to be taken over a long period of time. Species are also easier to conceptualize and have been the basis of much of the evolutionary and ecological research that biodiversity draws on. Species are well known and are distinct units of diversity. Each species can be considered to have a particular "role" in the ecosystem, so the addition or loss of single species may have consequences for the system as a whole.
Conservation efforts often begin with the recognition that a species is endangered in some way, and a change in the number of species in an ecosystem is a readily obtainable and easily understandable measure of how healthy the ecosystem is.
This is the least visible and, arguably, least studied level of biological diversity. Genetic diversity is the variety present at the level of genes. Genes, made of DNA, are the building blocks that determine how an organism will develop and what its traits and abilities will be. This level of diversity can differ by alleles different variants of the same gene, such as blue or brown eyes , by entire genes which determine traits, such as the ability to metabolize a particular substance , or by units larger than genes such as chromosomal structure.
The amount of diversity at the genetic level is important because it represents the raw material for evolution and adaptation. More genetic diversity in a species or population means a greater ability for some of the individuals in it to adapt to changes in the environment. Less diversity leads to uniformity, which is a problem in the long term, as it is unlikely that any individual in the population would be able to adapt to changing conditions.
As an example, modern agricultural practices use monocultures, which are large cultures of genetically identical plants. This is an advantage when is comes to growing and harvesting crops for example all the plants can be harvested at once , but can be a problem when a disease or parasite attacks the field, as every plant in the field will be susceptible.
Monocultures are also unable to deal well with changing conditions. Within species, genetic diversity often increases with environmental variability, which can be expected. If the environment often changes, different genes will have an advantage at different times or places. In this situation genetic diversity remains high because many genes are in the population at any given time.
If the environment didn't change, then the small number of genes that had an advantage in that unchanging environment would spread at the cost of the others, causing a drop in genetic diversity. Since the gene is the fundamental unit of natural selection, and thus of evolution, some scientists argue that the real unit of biodiversity is genetic diversity. However, species diversity is the easiest one to study. Ecosystem diversity deals with species distributions and community patterns, the role and function of key species, and combines species functions and interactions.
The term "ecosystem" here represents all levels greater than species: This is the least-understood level of the three described here due to the complexity of the interactions. Trying to understand all the species in an ecosystem and how they affect each other and their surroundings while at the same time being affected themselves, is extremely complex. Difficulties in Examining Ecosystem Diversity.
The enormous range of terrestrial and aquatic environments on earth has been classified into a number of ecosystems. Major habitat types include tropical rain forests, grasslands, wetlands, coral reefs and mangroves. Measuring changes in the extent of ecosystems is difficult, because there is no globally agreed classification of ecosystems.
Thus, ecosystems can be considered on different scales. Transitions between them are usually not very sharp.
What is biodiversity and why does it matter to us?
Biodiversity: Biodiversity, the variety of life found in a place on Earth or, often, the total variety of life on Earth. A common measure of this variety. Biodiversity definition is - biological diversity in an environment as indicated by numbers of different species of plants and animals. Did You Know?. We provide definitions and key words used in Hawke's Bay biodiversity work from a New Zealand and global perspective.