Biodiversity Variety of life

Why is it important to conserve biodiversity? We depend on it for food fuel clothing building materials medicines Aestetic value Cultural value And more

“At least 40 per cent of the world’s economy and 80 per cent of the needs of the poor are derived from biological resources. In addition, the richer the diversity of life, the greater the opportunity for medical discoveries, economic development, and adaptive responses to such new challenges as climate change” http://www.youtube.com/watch?v=EGMkW_vo5GU#t=13

Measuring biotic components of the system Methods for estimating abundance of organisms. The mark/release/recapture technique and the Lincoln index for estimating the abundance of motile species. Quadrats for measuring population density, % frequency and % cover of stationary species (plants).

Measuring diversity of an ecosystem Diversity refers to the heterogeneity of an ecosystem. It may be related to the diversity of species, habitats or genetics within a specific unit area. Diversity of species or biodiversity, is a measure of the variety of species per unit area. And is defined as “the amount of biological or living diversity per unit area.” Biodiversity of an ecosystem is expressed numerically by applying a biodiversity index.

Diversity Indices There are various different diversity indices that can be used to estimate biodiversity of particular areas. They are based on: Proportional abundance of species (Shannon’s Index and Brillovin’s Index) Species richness (log series Index, Margalef’s Index and Menhinick’s Index) Species richness and relative abundance (Simpson’s Index and Berger-Parker`s Index)

Species richness and relative abundance. Species richness (s) = the total number of species present. Relative abundance = the number of individuals per species. Diversity often just refers to the species richness of an area (Margalef’s Index) a more useful measure of a community characteristic is when species richness is combined with the relative abundance of species present (Simpson`s Index).

The Simpson’s Index D = N(N-1) ∑n(n-1) D = diversity index N = total number of organisms of all species found. n = number of individuals of a particular species. ∑ = sum of. A high value for D suggests a stable and ancient site and a low value of D could suggest pollution, recent colonization or agricultural management.

To demonstrate the importance of species richness and relative species abundance Case study 1. Environmentalists carried out a survey to compare the diversity of 2 different streams to determine if the presence of an industrial outlet into one of the streams (stream 1) has had any effect on the species diversity. First they counted the number of different species present Stream 1: 175 animals sampled consisting of 16 different species Stream 2: 100 animals sampled consisting of 10 different species This gives an idea of species richness, from which it could be concluded that stream 1 is the more diverse, and that diversity has not been adversely effected by industrial pollution However it does not reflect how many of each species are present. Therefore the environmentalists counted and recorded the number of individuals for each species found in the streams.

To demonstrate the importance of species richness and relative species abundance. Stream 1 Stream 2 1 85 10 2 6 3 4 5 7 8 9 11 12 13 14 15 16 Work out the diversity of each stream by applying the Simpson's index to each site D = N(N-1) ∑n(n-1)

Stream 1 N = 175 D= 175 x 174 Stream 2 N = 100 D = Finish applying the formula for streams 1 and 2 to find D = N(N-1) ∑n(n-1) Stream 1 N = 175 D= 175 x 174 (85x84)+ (6x5)+ (6x5)+ (6x5)+ (6x5)+ (6x5)+ (6x5) + (6x5)+ (6x5)+ (6x5)+ (6x5)+ (6x5) = Stream 2 N = 100 D =

Species Stream 1 (n) Stream 2 Stream 1 n(n-1) Stream 2 n(n-1) 85 10 7140 90 2 6 30 3 4 5 7 8 9 11   12 13 14 15 16 ∑n(n-1) 7590 900 N 175 100 N(N-1) 30450 9900 D 4.01 11.00

Conclusion By applying information about the species richness (N) and the relative species abundance (n) to the Simpson’s biodiversity index it is possible to give numerical values to the streams. D for stream 1 is 4.01 D for stream 2 is 11.0 Which stream has the lowest biodiversity? Based on these values which stream would you expect to be polluted by industrial waste? Could the environmentalists therefore conclude that the factory is polluting and damaging the environment? Explain your answer.

Example 2 Assume that you have studied a particular habitat and you have recorded the types of 20 animals you have found. The different types are represented by letters of the alphabet and the record shows five species: AAAABBACCBBABBADCCDE By applying the Simpson’s Index calculate diversity of this habitat?

Species number of animals (n) Stream 1 n(n-1) 7 42 B 6 30 C 4 12 D 2 E 1 ∑n(n-1)   86 N 20 N(N-1) 380 4.42 The diversity of this habitat is 4.42

Example 3 The Simpson index was used to calculate the diversity of an oak wood and a conifer plantation. The values obtained were 19.6 for the oak wood and 12.04 for the conifer plantation. Which habitat is the more diverse? Explain why there is such a difference in diversity between these 2 ecosystems?

The oak wood is more diverse than the conifer plantation. Oaks grow in more temperate regions where the climate will allow more species to survive, compared to the more extreme climatic conditions where conifers grow, which limit species to those that are adapted to cold, dry conditions. Oak woods are examples of more established, older woodlands where more species have had the opportunity to adapt to the environment. Conifer plantations consist of relatively fast growing trees which quickly establish and are cut down before other species have the chance to colonize the conifer ecosystem. Although oaks are the dominant species there are usually other tree species in an oak wood such that there are many more habitats available for a more diverse variety of species. Compared to the conifer plantation which is a man made monoculture where only one species of tree has been planted. Light intensity. Conifer plantations are usually planted relatively closely together and their dense growth limits the amount of light passing through the needle canopy. Thus limiting the number of plants that may survive. Conifers leave a dense mat of needles on the ground which limits the ability of seeds to establish themselves as growing plants. Also the needles may alter the chemistry of the soil causing the unfavourable conditions.

Using the Simpson’s Index Diversity indices are an important means for comparisons of community structure and stability. It is useful when investigating the interaction of abiotic and biotic factors of an ecosystem. Diversity in ecosystems is equated with stability and climax communities. Most stable communites have a large number of different species with relatively similar numbers of organisms in each (high D.I). Whereas ecosystems under stress have few species which become abundant and low diversity (low D.I.) To assess the influence of man on diversity of species, for example due to deforestation, desertification, urbanisation and pollution. To compare biodiversity in different habitats, ecosystems, biomes, communities etc.