Species richness

Global mammal richness (2015)

Species richness is the number of different species represented in an ecological community, landscape or region. Species richness is simply a count of species, and it does not take into account the abundances of the species or their relative abundance distributions. Species richness is sometimes considered synonymous with species diversity, but the formal metric species diversity takes into account both species richness and species evenness. Species richness has proven to be a positive representation to show how species interaction in ecosystems can lead to the productivity and growth of biodiversity.

Habitual interactions among aquatic species.

Biodiversity is an imperative factor used to connect both species richness and species evenness to detect relatedness where genetics, relative species abundances and ecological distributions is concerned. The higher biodiversity there is within an ecosystem, the higher the chances are that species richness will be prevalent with respects to the ecosystem's relative abundance levels. Species richness across different parts of the world will show variations based on location, climate, predator/prey relationship, food availability and other factors that lies in the throes of environmental influences. The image below shows a representation of an aquatic relationship among members of the same community. Competition for food, mating spaces, and overall predator or prey relationship can also arise. An abundance in the number of species will present itself where habitats are relatively available for species to live, where competition and predators are not actively seeking to lower their abundance levels.

The Connection Between Species Richness and Diversity

Biodiversity Pyramid

As previously mentioned, biological diversity also known as biodiversity is the variation living things and how their interactions with each other affect life on Earth. With biodiversity, there are few things that contribute to the life on Earth. One of those things are species such as new species being discovered or species becoming extinct. Since species richness is represents the number of species living in space, it plays apart in not only biodiversity but with species diversity as well. Knowing the number of species in a space is very essential when looking on the different livings things that contribute to the diversity of either Earth or within a certain living space because we can observe the changes that is constantly occurring throughout life. When using species richness to compare the diversity, there are few factors that needs to be considered. Those factors include looking at the overall and the relative abundance of the individual within the species group and where the species in the living space are mostly found.   Without those factors, it would be hard to determine the diversity of species.

Sampling considerations

Depending on the purposes of quantifying species richness, the individuals can be selected in different ways. They can be, for example, trees found in an inventory plot, birds observed from a monitoring point, or beetles collected in a pitfall trap. Once the set of individuals has been defined, its species richness can be exactly quantified, provided the species-level taxonomy of the organisms of interest is well enough known. Applying different species delimitations will lead to different species richness values for the same set of individuals.

In practice, people are usually interested in the species richness of areas so large that not all individuals in them can be observed and identified to species. Then applying different sampling methods will lead to different sets of individuals being observed for the same area of interest, and the species richness of each set may be different. When a new individual is added to a set, it may introduce a species that was not yet represented in the set, and thereby increase the species richness of the set. For this reason, sets with many individuals can be expected to contain more species than sets with fewer individuals.

If species richness of the obtained sample is taken to represent species richness of the underlying habitat or other larger unit, values are only comparable if sampling efforts are standardized in an appropriate way. Resampling methods can be used to bring samples of different sizes to a common footing. Properties of the sample, especially the number of species only represented by one or a few individuals, can be used to help estimating the species richness in the population from which the sample was drawn. These indications and adaptations to the detail of population enhancements can provide further diversity in urban ecological areas by means of promoting species richness while also considering the ecological community.

Trends in species richness

The observed species richness is affected not only by the number of individuals but also by the heterogeneity of the sample. If individuals are drawn from different environmental conditions (or different habitats), the species richness of the resulting set can be expected to be higher than if all individuals are drawn from similar environments. The accumulation of new species with increasing sampling effort can be visualized with a species accumulation curve. Such curves can be constructed in different ways. Increasing the area sampled increases observed species richness both because more individuals get included in the sample and because large areas are environmentally more heterogeneous than small areas.

Many organism groups have most species in the tropics, which leads to latitudinal gradients in species richness. There has been much discussion about the relationship between productivity and species richness. Results have varied among studies, such that no global consensus on either the pattern or its possible causes has emerged. Species diversity and richness is likely to occur in areas of warmer climates because of variability in food types, mating opportunities, urban area provision of cleaner environments and other factors that can lead to an improved species richness.

Species richness also depicts immense extension by means of expanding in terms of ecological and environmental availability of urban food types which enriches the likelihood of species richness increasing even in urban areas; additionally, increasing food availability in certain environments will provide better chances of species richness in terms of diversity. Where there is food, there are animals according to the balance of nature or the ecological balance as it is generally known, which expresses types of food chain and food webs which are both used in urban ecology to show the differences but mostly similarities in which feeding relations between species can be understood. Every type of species will consist of their individual type of feeding relationship with organisms provided by the environment, however, it is necessary to understand that feeding relationships and the urban species will indeed form a type of symbiotic relationship within an ecosystem according to urban necessities as shown in the image provided.

Feeding Relationship

Applications

Species richness is often used as a criterion when assessing the relative conservation values of habitats or landscapes. However, species richness is blind to the identity of the species. An area with many endemic or rare species is generally considered to have higher conservation value than another area where species richness is similar, but all the species are common and widespread.

Location-wise, urban settings can influence species richness by means of proper environmental conservation, availability of safety and other factors like water, trees, and sustainable habitat. Species thrives in areas where they are provided with the basic necessities for their survival, even in urban areas where they may face challenges like competition or predators, they still have a high chance of surviving when placed in an environment that provides adequate resources that can benefit the species and promote species diversity and richness.

With food-web in mind, species richness in either aquatic or non-aquatic environments can serve as either predator or prey for some animals. In this case, it is possible for species richness with respect to species evenness to form a negative outcome when the relative species abundance is threatened. There can also be a negative or positive impact on species diversity, this can also influence how species richness in an area will affect their environment. Since some environments thrives off of species interactions, it can pose an undesired consequence whereby the community itself is impacted by the loss of species.

Species richness and urban ecology

Urban ecology and species richness commonly coincides based on the location, availability of resources, suitable temperature, access to water and other factors like typical wildlife of all sorts. The richness and abundance of species are the starting elements that promotes the growth and survival of urban ecological life, without the community's input, it may be difficult to accurately represent an urban life if certain accommodations are not met. Urban ecology always starts as an interactive relationship between species and surroundings to show an interconnected type of relationship between species richness and the response of the environment.

Global urban development has been established to increase the likelihood of both humans and different types of species living together in harmony not just for the benefit of the world, but for each individual ecosystem. When humans and animals work together, species diversity can benefit whereby animals can freely exist in their own world without the fear of being slaughtered just for coexisting with humans and humans can also benefit from the help of animals. It is not always impossible for humans and animals to exist in the same space, with the help of humans; species can be able to live in peaceful neighborhoods or habitats within their own biodiversity, all this does is increase the likelihood of species richness and an abundance of population growth.

Additionally, with the concept of species richness, species abundance, population growth and diversity in mind, it is crucial to understand that urban ecology has not always been stable when change is constant. Environmental and ecological resilience has played major roles in the re-development of habitats, ecosystems, biomes and their impacts and adjustments to urbanization, change is a necessary factor where species richness is concerned and attached to the environmental and ecological growth and development across the globe. Change is inevitable, and for the sake of species richness, it's necessary that they are all exposed to places and communities they can have positive connections with, not only for the benefit of the now, but for their future generations.

An example of an urbanization area

Species richness can be affected by urbanization. Since urbanization involves improve areas to make more modern that means that the areas will undergo changes to better life for some humans but the other living species such as animals will not get the same benefits as humans. When people think of urbanization, they don't think about how it affects the species in the soil. It can be observed that species richness within the soil will decrease as urbanization develops due to the environment changes. For instance, an experiment was conducted to see how the soil species with the high ability and low ability to move throughout the soil were affected due to the changes that came with urbanization. The result was that the species that had low ability of movement and medium ability of movement such as snails and annelids was affected by urbanization drying out the soil, which limited the species movement. The drying of the soil causes those species mentioned, to find a new space with soil that is moist to help move through the soil. In conclusion, species richness is affected by how urban the area is. The more urban, the less the richness of the species depending on if the species are adjusted to new changes in their home is there and vice versa.

See also

• Rapoport's rule
• Scaling pattern of occupancy
• Species-area curve
• Species discovery curve
• Storage effect

Further reading

• Kevin J. Gaston & John I. Spicer. 2004. Biodiversity: an introduction, Blackwell Publishing. 2nd Ed., ISBN 1-4051-1857-1(pbk.)
• Diaz, et al. Ecosystems and Human Well-being: Current State and Trends, Volume 1. Millennium Ecosystem Assessment. 2005. Island Press.