Chapter 11

Biodiversity is the variety of all living organisms presemt in an area. Biodiversity is essential in maintaining a balanced ecosystem for all organisms, as all species depend on one another, eg trees provide habitatss for animals, fungi decompose dead organic matter, making fertile soil for plants to grow for animals to eat, if one thing affects the biodiversity of an ecosystem, it will eventually harm all the species present. We rely on balanced ecosystems to produce all the food, oxygen and nutrients we need to survive.

Tropical moist regions have the most biodiversity, and very cold or dry areas have the least biodiversity. Generaly speaking the closer you get to the equator the greater the biodiversity is. Measuring biodiversity is important in conservation as it informs scientists what species are present producing a basseline level of biodiversity in an area, from this the effect on changes on th environment can be measured, such as human activity, climate change or disease. Before a major project is undertaken, an Environmental Impact Assesement is undertaken to predict the positive and negative effects of the project on the biodiversity in that area. Biodiversity can be studied in 3 different areas: Habitat biodiversity, species biodiversity and genetic biodiversity.

Habitat biodiversity: This refers to the number of different habitats found within an area. Each habitat can support a number of different species so in general the greater tha habitat biodiversity, the greater the species biodiversity. The UK has a fair amount of habitat types like meadows, woods, and sand dunes, whereas places like Antarctica have a very low habitat diversity.

Species biodiversity: Species biodiversity has 2 different components: Species richness - the number of species living in a particular area, and species eveness - a comparision of the numbers of individuals of each species living in a community. Therefore an area can differ in its species biodiversity even it has the same number of species, depending on how balanced the populations are and the relevant percentage of each species within an area.

Genetic biodiversity: This refers to the variety of genes that make up a species, although many are the same for all members of a species, for many genes different alleles exist leading to genetic biodiversity which can lead to quite different characteristics being exhibited. Greater genetic biodiversity allows for better adaptation to a changing environment, and is more likely to result in individuals who are resistant to disease.

Sampling is where measurements of a limited number of individual organisms are taken in a particualr area, and is used to measure and compare the biodiversity of different habitats. Sampling can also be used to measure a particular characteristic of an organism, and use it to calculate an avergae. After measuring a sample you can use the ressults to make generalisations or estimates about the nuber, distribution or measured characteristic of an organism throughout an entire habitat. 

Random sampling means selecting individuals by chance, and each individual in a population has an equal likelyhood of selection. Random numbers can be used to generate co ordinates which are then used to take samples along an x and y grid set out in an area. A sample is never entirely representative of the organisms presnt in a habitat which may be due to:

• Sampling bias - the selection process may be biased as conscious or subconscious decisions can affect the reliability of the sample, the effects of this can be reduced using random sampling where human involvement in choosing the samples is removed.
• Chance - the organisms selected may, by chance, not be representative of the population, this can never be fully removed from the process but its affects can be minimised by using a large sample size as the greater number of individuals studies, the lower the probability that chance will influence the result, so large the sample size, the greater the reliability.

Non-random sampling can be divided into 3 main techniques:

• Oppertunistic - this is the weakest form of sampling as it may not be representative of the population, as it uses the organisms that are conveniently available
• Stratified - some populations can be divded into sub group strata based on a particular characteristic, and then a random sample is taken from each of these strta proportional to its size.
• Systematic - in systematic sampling different areas within an overall habitat are identified which are then sampled seperately. For example systematic sampling may be used to show how plant species change as you move inland from the sea. Systematic sampling is often carried out usig a line or belt transect where samples are taken at regular intervals between two points, a belt transect provided more information as samples are talen of the area between the two parallel lines.

The follwing techniques can be used to collect living animals for study:

• A pooter is used to catch small insects by sucking them into a holding chamber whilst a filter on the mouth piece prevents them from being sucked into the mouth.
• Sweep nets are used to catch insects in areas of long grass.
• Pitfall traps are used to catch small crawling invertebrates where a hole is dug in the ground which insects fall into, it must be deep enough that they cannot crawk out and needs to be covered with a roof structure sp the trap doesn't fill with rainwater, the traps are usualy left overnight so that nocturnal species are also sampled.
• Tree beating is used to take samples of the invertebrates living in a tree or bush, a white cloth is spread under the tree and then the tree is shakem to dislodge the invertebrates.
• Kick sampling is used to study the organisms living in a river, the river bank and bed is kicked for a period of time to distirb the substrate and then a net is held downstream for a set period of time to capture organisms released into the flowing water.

Plant are normally sampled using a quadrat which can also be used to pinpoint an area in which the sample of plants should be collected, they can also be used to sample slow moving animals such as limpets and barnacles. The two main types of quadrat are a point quadrat - which consists of a frame and a horizontal bar where set intervals on it have pins which can be pushed through to reach the groun where each species of plant touching the pin is recorded. The other type is a frame quadrat - which consists of a square frame divided into a grid of equal of equal sections where the type and number of species in each section is recorded. Quadrats should be used following random sampling techniques, or systematically along a line or belt transect to study the distribution of organisms across an area of land varies.

To measure species richness you should use a combination of techniques to try and identfiy all the species present in a habitat and a list of each species should be compiled. This often involves the use of identification keys to help classify the organisms based on identifiable characteristics. This can also be used to work out the proportion of each species in comparision to each other to measure species eveness.

A frame quadrat is used to sample the population of plants living in a habitat, there are 3 main ways of doing this:

• Density - if individual large plants can be seen clearly, count them in numbers per each sqaure of the quadrat, and this is an absolute measure not an estimate like the other methods.
• Frequency - this is used where individual members of a species are hard to count, like grass or moss. Using the small grids within a quadrat, count the number of squares a particular species is present in, and this acts as a percentage frequency.
• Percentage cover - this is used for speed as lots of data can be collected quickly, it is useful when a particular species is abundant or difficult to count, it is an estimate by eye of the area within a quadrat that a particular plant species covers.

For each approach, samples should be taken at a number of different points as this increases the reliability of results, and then calculate the mean of the individual quadrat results to get an average value for an organism per metre squared.

As animals are constantly moving through a habitat and others may be hidden, it can be difficult to accurately determine their population size. The capture mark release recapture method is often used where as many individuals of a species in an area as possible are captured and marked, and after time taken into account for redistribution another sample of animals is collecyed. By comparing the number of marked individuals to the number of unmarked individuals you can estimate population size. The greater the number of marked individuals recaptured, the smaller the population. The species eveness in an area can then be calculated by comparing the total number of each organism present, populations that are similar in size or density represent an even community and hence a high species eveness, which can also be represented as a ratio between the numbers of each organism present.

Abiotic factors are the non living conditions in a habitat and have a direct effect on the living organisms that reside there such as light and water availibility, scientists usually measure them using sensors so they can draw conclusions about the species present and the conditions thet need for survival. Sensors alllow rapid changes to be detected, human error in readings is reduced, a high degree of precision can be achieved, and data can be stored and tracked on a computer.

One way to measure biodiversity is to calculate the species diversity as this is normally proportional to the stability of an ecosystem, the greater the species diversity the greater the stability. Pollution often reduces biodiversity as harsh conditions lead to a few species being dominant in an ecosystem. The smiplest way to calculate biodiversity is to count up the number of species present, but this does not take into account the number of individuals present. Simpson's Index of Diversity (D) is a better measure of biodiversity as it takes into account both species richness and species eveness. N = the total number of all species and n = the total number of organisms of a particular species. When using this equation scientists normally have to estimate population size and a variety of sampling techniques. Simpson's Index of Diversity always results in a value between 0 and 1, where 0 represents no diversity and 1 represents infinite diversity, the higher the value, the higher the diversity.

Althought some habitats of low biodiversity are able to support a large species diversity, those organisms can be highly adapted to the extreme environment and not survive elsewhere. It is therefore important to conserve some habitats with a low biodiversity.

Maintaining genetic biodiversity is essential for the survival of a species, and the gene pool can be used to monitor the health of the population and ensure long term survival. Within a species, indiviuals have very little variation within their DNA, all members of the species share the same genes, but they may have different alleles, the differences in these amongst the individuals of a species creates genetic diversity within the species. Species that contain greater genetic biodiversity as a result of more alleles are more likely to be able to adapt to changes in their environment and hence are less likely to become instinct. This is because there are likely to be some organisms within the population that carry an advantageous allele which will enable them to survive in the altered conditions and are more likely to reproduce leading to the survival of a species, such as individual who is resistant to a new potentially fatal disease.

 For genetic biodiversity to increase, the number of possible alleles in a population must increase, this can happen as a result of:

• Mutation(s) in the DNA of an organism, creating a new allele.
• Interbreeding between different populations - When an individual migrates from one population and breeds with a member of another population, alleles are transferred between the two populations. This is known as the gene flow. 

In order for genetic biodiversity to decrease, the numer of possible alleles in a popluation must also decrease which can occur through:

• Selective breeding - this is where only a few individuals within a population are selected for their advantageous characteristics and bred, such as for food.
• Captive breeding programmes - here only a small number of captive individuals of a species are available for breeding as often the wild populatgion is endagered or extinct.
• Rare breeds - selective breeding results in certain characteristics becoming unpopular, the numbers of the breed fall dramatically and when only a small number of individuals are left for breeding, genetic biodiversity will be low, which can cause major problems qhen trying to restore numbers yet maintain breed characteristics.

• Natural selection - as a result species will evolve to contain primarily the alleles which code for advantageous characteristics, and over time allales coding for less advantageous characteristics will be lost from a population or only remain in a few individuals, decreasing genetic biodivesity.
• Genetic bottlenecks - this is where a few individuals within a population survive an event or change, thus reducing the gene pool as only the alleles of the surviving members of the population are available to passed on to offspring.
• The founder effect - this is where a small number of individuals create a new colony, geographically isolated from the original, so the gene pool for this population will be small.
• Genetic drift - due to the random nature of alleles being passed on from parents to their offspring, the frequency of occurence of an allele will vary, and in some cases the existence of a particular allele will disappear altogether. Genetic drift is more pronounced in populations witha low genetic biodiversity.

One way in which scientists quantify genetic biodiversity is by measuring polymorphism. Polymorphic genes have more than one allele, for example, different alleles exist for the immunoglobulin gene which plays a role in determining human blood types. Most genes are not polymorphic but monomorphic where only a single allele exists for this gene, this ensures that the basic structrue of an individual within a species remains consistent. The proportion of genes that are a polymorphic can be measured using the formual

propotion of polymorphic gene loci = number of polymorphic gene loci/total number of loci

The greater the proportion, the greater the genetic biodiversity within the population.

Maintaining biodiversity is essnetial for preserving a balanced ecosystem for all organisms, as species are interconnected within an ecosystem so the removal of one species can have a profound effect on others. The human population is growing at a dramatic rate due to improvoements in hygeine, medicine and infrastructure. To create enough space for housing, industry and farming to support the increasing population, humans are the leading cause of loss of biodiversity as a result of:

• Deforestation - the permanent removal of large areas of forest to provide wood for buildings and fuel, and to create space for raods, buildings and agriculture.
• Agriculture - an increasing amount of land has to be farmed in order to feed the growing population, this has resulted in large amounts of land being cleared and in many cases planted with a single crop (monoculture).
• Climate change - there is much evidence that the release of carbon dioxide and other pollutants as a result of burning fossil fuels is increasing global temperatures.

Other forms of pollution result from industry and agriculture, such as improper disposal of waste and packaging or chemical pollution in waterways.

Deforestation can occur naturally through forest fires caused by dry weather, but most of it occurs deliberately as a result of human action and affects biodiversity in a number of ways:

• It directly reduces the number of trees present in an area.
• If only a specific type of tree is felled, the species diversity is reduced.
• It reduces the number of animal species present in an area as it destroys their habitat, including their food source and home, which in turn reduces the number of other animal species present by reducing or removing their food source.
• Animals are forced to migrate to other areas to ensure their survival, which result in an increased biodiversity in a neighbouring area, or may increase competition in that area.

In some areas forests are now being replaced, which can help restore biodiversity but generally only a few commercially viable trees are planted, so biodiversity is still significantly reduced from its original level.

In general, farmers will only grow a few different species of crop plants or rear a few species of animal as they will be selected based on characteristics that give a high yield. In order to be economically viable, farmers use a number of techniques to maiximise food production, but these techniques often lead to a reduction in biodiversity, for example:

• Deforestation - to increase the area of land available for growing crops or rearing animals.
• Removal of hedgegrows - as a result of mechnisation, farmers remove hedgegrows to enable the use of large machinery, this reudces the number of plant species in an area and removes the habitat of animals such as birds, hedgehogs and mice and many invertebrates.
• Use of chemicals such as pesticides. Killing pests reduces species diversity directly as it destroys the pest species and those that would use the pest species as a food source.
• Herbicides are used to kill weeds as they compete with the cultivated plants for light,minerals and water. By destroying weeds plant diversity is reduced directly and indirectly.
• Monoculture - many farms specialise in the production of only one crop, which massively lowers local biodiversity as one plant species will only support a few animal species and results in overall low biodiversity levels. Such as the growth of palm oil plantations causing major deforestation leading to a loss of habitat for endagered species such as the rhino.

Key findings on the current understading of climate change include:

• The warming trend over the last 50 years is twice that for the previous 100 years.
• Average amount of water vapour in the atmosphere has increased due to warmer air.
• Average temperature of the global ocean has increased as the ocean has been absorbing mote than 80% of the heat added to the climate system, causing rising sea levels.
• The global sea level is rising at a greater rate than from previous centuries.
• Average Arctic temperatures have increased twice the average rate in the past 100 years.
• Mountain glaciers and snow cover have declined in both hemispheres, and widespread decrease in glaciers and ice caps have contributed to sea level rise.

To enable our understanding of climate change to develop, significant data needs to be collected as a result of international co operation due to its global implications for the future, and the need to produce reliable evidence for the link between human activity and global warming is paramount. 

If global wartming continues biodiversity will be affected, For example:

• The melting of the polar ice caps could lead to the extinction of the few plant and animal species living in that region, and manty migrate further north as their habitat shrinks. Increasing gloval temperatures would allow temperate plants to live further north.
• Rising sea levels from melting ice caps and the thermal expansion of oceans could flood low lying land resulting in the loss of terrestrial habitats, saltwater would flow further up rivers, reducing the habitats of freshwater plants living in the river and the surroundign areas.
• Higher temperatures and less rainfall would result in some species failing to survive, leading to drought resistant becoming more dominant. The loss of non drought resistant species would lead to the loss of some animal species dependant on them as a food source. These would be replaced by other species that feed on the xerophytes.
• Insect life cycles and populations will change as they adapt to climate change, insects are key pollinators so if the range of insects changes, it could affect the plants it leaves behind. Moreover if tropical insects spread this could lead to the spread of tropical disease.

If climae chang is slow then species may have time to adapt or migrate, which would not necessarily lead to loss of biodiversity, the species mix would simply change.

The reasons for maintaining biodiversity can be arranged into 3 groups:

Aesthetic reasons: 

• The presence of different plants and ainimals enriches our lives.
• The natural wordl provides inspiration for musicians, artists and writers, who in turn provide many pleasures through music, art and books.
• Studies have shown that patients recover more rapidly from stress and injury when surrounded in the natural environment.

Economic reasons - if biodiversity in an ecosystem is maintained , productivity is higher:

• Soil erosion and desertification occur as a result of deforestation, which reduced a country's ability to grow crops and feed its people, leading to dependance on other nations.
• It is important to conserve all organisms we use to make things, as non sustainable removal of resources will lead to the collapse of those industries as once the raw material is lost it no longer becomes economically viable to continue the industry. Even 'sustainable' methods never replace as much biodiversity as the established habitats had prior to replacement.

• Large scale habitat losses mean that species with potential economic importance may become extinct before they are even discovered, for example many undiscovered plant species in the rainforest may be chemically or medically useful.
• Continuous monoculture results in soil depletion - a reduction in the diversity of soil nutrients happens because the crop takes the same nutrients out of the soil each year and the nutrients are not left o be recycled, and this depletion of nutrients makes the ecosystem more fragile. The crops it can support will be weaker, increasing vunerability to pests and weeds, and the farmers will become increasnigly independant on expensive fertilisers, pesitcides, and herbicides in order to maintain productivity.
• High biodiversity provides protection against abiotic stresses and disease. when biodiversity is not maintained a chnage in conditions or a disease can destroy entire crops as the smaller gene pool will result in a lower chance of any alleles that are resistant to the change.
• The greater the diversity in an ecosystem, the greater the potential for the manufacture of different products in the future, and these products may be beneficial to humans.

• Plant varieties are needed for cross breeding, which can lead to better characteristics such as disease resistance or increased yield. The wild relatives of cultivated crops privde a massive reservoir of genetic material tp aid the production of new variteties of crop. Through GMO scientists alos aim tp use genes from wild plants and animals to make crop plants and animals more efficient. reducing the land required to feed more people. If these wild varieties are lsot, the ctop plants themselves may become vunerable to extinction.

Ecological reasons:

• All organisms are interdependant on others for survival. The removal of one species may have a significant effect others, for example decomposers break down dead plant and aniaml remains, releasing nutrients into the soil which plants later use for healthy growth..
• Some species play a key role in maintaing the structure of an ecological community, and have a disproportionatelt large effect on their environment relative to their abundance, they affect many other organisms in an ecosystem and help determine species richness and eveness. When a keystone species is removed the habitat is drastically changed and some species may disappear altogether, it is essential to protect a keystone species to maintain biodiversity.

Human activity can also have an important role in increasing biodiversity, as in many countries such as the UK the natural habitatis created by human intervention and management of land. For example sheep grazing on downlands, by keeping the grass at low levels it allows the plantains that the catipillars feed on to thrive and therefore maintains biodiversity, as some environments when left on their own can develop so that one species is dominant, lowering biodiversity of that area. For example areas of low level heath are rarer than rainforest and provude habitats for rare birds and reptile species in the UK.

Sea stars are an example of a keystone species, they are predators that maintain a balanced ecosystem by limiting the population of other species, such as sea urchins which have no other natural predators, if sea stars are removed, their is a population explosion of its prey that prevents other species from occupying the same area.

It is estimated that over 200 species rely on prarie digs, as their tunnels provide burrows for other animals like snakes and their droppings lead to redistribution of nutrients. Moreover the tunnels channel rainwater into the water table, so provide a massive significance in these ecosystems.

Conservation is the name given to the preservation anf careful management of the environment and of natural resources, as by conserving the natural habitat in an area, organisms' chances of survival are maintained allowing them to reproduce, so species and genetic diversity can be safeguarded. The main two catergories of conservation are in situ conservatiom - within the natural habitat, and ex situ conservation - out of the natural habitat. Scientists are currently trying to conserve a number of species to prevent their extinction, species are classified according to their abundance in the wild as:

• Extinct - no organisms of that species exist anywhere in the world.
• Extinct in the wild - organisms of the species only exist in captivity.
• Endagered - a species is in danger of extinction
• Vunerable - a species that is considered likely to become endangered in the near future.

Non threatened and least concern categories follow below. Many conservation techniques focus on increasinf the number of organisms that are endagered. Scientists alos practive sustainable development - meeting the needs of the people today without limiting the availability of future generations to meet their needs.

In situ conservation takes place inside an organism's natural habitat which maintains the genetic diversity of species but also the evolutionary adaptations that enable a species to adapt to a continually to changing environmental conditions. By allowing the species to interact with other species, it alos preserves the interdependant relationship present in a habitat, so interlinked species may also be preserved. This type of conservation is usually cheaper. Specific reserves are examples of areas that have been designated for conservation, such as widlife reserves where active management techniques include:

• Controlled grazing - only allowing livestock to graze in a particular area of land for a certain period of time allows species time to recover, or keeping a controlled number of animals in a habitat to maintain it.
• Restricting human access - Eg not allowing people to visit a beach during the seal reproductive season or providing paths which must be followed to prevent plants being trampled.
• Controlling poaching - this includes creating defences to prevent access, issuing fines or more drastic steps such as the removal of rhino horns.
• Feeding animals - this  can help ensure more organisms survive to reproductive age.
• Reintroduction of species - adding species to areas that have become locally extinct, or whose numbers have decreased significantly.

• Culling or removal of invasive species - an invasive species is an organism that is not native to an area and has negative effects on the economy, environment or health. These organisms compete with native species for resources.
• Halting succession - succession is the natural process in which early colonising species are replaced over time until a stable mature population is achieved. For example any piece of land let along for long enough in the UK will develop intp woodland, and the only way to protect some habitats like heath and lowland is through controlled grazing, as animals eat tree seedlings as they appeal preventing succession. This is an important role played by humans in maintaining habitats for future generations.

Marine conservation zones are less well established than terrestrial ones, but are vital in preserving species-rich coral reefs that are being devastated by non sustainable fishing methods. The aims of conseravtion here are to create areas of refuge within which populations can build up and repopulate adjacent areas. Mrine reserves often need large areas as thr target species often travel long distances.

Ex situ involves the removal of organisms from their natural habitat, and is normally in addition to in situ methods to ensure the survival of a species.

Botanic gardens: Plant species can be grown successfully in botanic gardens. Here species are actively managed to provide the best resources to grow, such as the provision of soil nutrients, sufficient watering and the removal anf prevention of pests. Botanic gardens hold more than 10% of the world's flora, but the majority of species are not conserved. Many wild relatives of selectively bred crop species are under represented amongst conserved species.

Seed banks: A seed bank is an example of a gene bank - a store of genetic material. Plant seeds are dried and frozen to maintain their viability, almost all seeds can be stored in this way and provide a backup of against the extinction of wild plants by storing seeds for future reintroduction, research, breeding and genetic engineering. However seed banks don't work for all plant, sadly most of seeds of most tropical rainforest trees die when dried and frozen. 

Captive breeding programmes produce offspring of species in a human controlled environment, these are often run and maintained by zoos and and aqautic centres. Scientists working on captvie breeding programmes aim to create a stable, healthy populations of a speices and then gradually reintroduce it into its natural habitat. Captive breeding programmes provide the animals with shelter, an abundant supply of nutritious food, an absence of predators and vertinary treatment. Suitable partners or their semen for artificial insemination can be imported from other zoos around the world. Maintaining genetic diversity within a captive breeding population can be difficult as only a small number of breeding partners are available so problems relating to interbreeding can occur. To overcome this an internation catalogue is maintained that details the genetic data of individuals so mating can be arranged so that genetic diversity is maximised. Techniques such as artifical insemintation and emrbyo transfer allow new genetic lines to be introduced without having to transfer the animals or needing their co operation. Some organisms in captivity may not be suitable for release into the wild. Some of the reasons include:

• Diseases - there may be a loss of resistance to local diseases in captive bred populations, and new diseases might exist in the wild which captive animals have not yet developed a resistance to.

• Behaviour - some behaviour is innate, but much has to be learnt through copying or experience and some animals may not be able to survive in the wild due to domestication. For example in an early case of introduction in monkeys, a number of them starved because they had no concept of searching for food. Now food is hidden in cages to teach animals foraging skills.
• Genetic races - the genetic make up of captive animals can become so different from the original population that the two populations can no longer interbreed.
• Habitat - in many cases the natural habitat must first be resotored to allow captive populations to be reintroduced. If only a small suitable habitat exists it is likely there are already as many individuals as the habitat can support, and the introduction of new individuals can lead to stress and tension as individuals fight for limited territory and resources.

To conserve biodiversity successfully, local and international co operation is necessary, and cross-border protections should be offered. The Internation Union for the Conservation of Nature (IUCN) assists in securing agreements between nations. It is alos involved in setting up the CITES treaty that regulates the international trade of wild plant and animal specimens,and to safeguard certain species from over-exploitation.

The Rio Convention resulted in some new agreements between nations which include:

• The Convention on Biological diversity requires countries to develop national strategies for sustainable development and the maintennance of biodiversity.
• The United Nations Framework Conventiom on Climate Change is an agreement between nations to take steps stabilise greenhouse gas concentrations in the atmosphere.
• The Unite Nations Framework Convention to Combat Desertification aims to prevent the transformation of fertile land into desert and reduces the effects of drought.

Each convention contributes tp maintaining biodiversity and thet are intrinsically linked, operating in many ecosystems and addressing many interdependant issues.

Many conservatoin schemes are set up at a more local level such as the Countryside Stewardship Scheme in England. This scheme offered governmental payments to farmers and land managers to enhance and conserve the English landscape, its general aims being to make conservation a part of normal farming and land management practice. Specific aims of the scheme include:

• Sustaining the beauty and diversity of the landscape.
• Improving, extending and creating wildlife habitats.
• Restoring neglected land and conserving archaeological and historic features.
• Improving oppertunities for countryside enjoyement.

This scheme has now be replaced by thr Environmental Stweardship Scheme which operates similarily.