4.2.1 Biodiversity

Biodiversity

• Biodiversity - a measure of the variation found in the living world, in terms of habitats, species and genetics
• Habitat - where an organism lives
• Species - a group of organisms that are very similar in appearance, anatomy, physiology, biochemistry and genetics and that can freely interbreed to produce fertile offspring
• Habitat diversity - the range of habitats in which different species live
• For instance: sand dunes, woodland, meadows and streams
• Species diversity - the range of organisms that can be found in a habitat
• Species richness - a measure of how many different species are present
• Species evenness - a measure of how evenly represented the species are
• Genetic biodiversity - variation between individuals belonging to the same species
• Genetic biodiversity creates different breeds within a species

Sampling

• Sampling is a way of measuring biodiversity in a habitat without needing to measure the whole habitat - saving time, money and resources.
• Random - sample sites inside habitat are randomly selected. Pros: no bias from selective sampling. Cons: may not cover habitat equally, species with a low presence may be missed
• Non-random, opportunistic - researchers makes sampling decisions based on prior knowledge, such as selecting an area known to have a particular species. Pros: easier and quicker than random sampling. Cons: data may be biased, leading to an overestimate of certain species
• Non-random, stratified - dividing a habitat into areas that appear different and sampling each one separately, in proportion to their incidence. Pros: all different areas are sampled & species less likely to be missed. Cons: may look at a lot of small areas which are all different
• Non-random, systematic - samples are taken at fixed intervals across the habitat. E.g. line & belt transects. Pros: Shows clear changes across a environmental gradient. Cons: species may be missed, leading to underestimate of biodiversity

Sampling plants and animals

• Sampling plants:
• Large plants (such as trees) can be counted individually. Small plants are best measured by percentage ground covered by each species. a quadrat (a square frame) defines the size of the sample area. A random number generator can be used to generate sets of coordinates to place the quadrat. Alternatively, a transect is a line taken across a habitat, which you use to measure changes in habitat and environment.
• Sampling animals: can present difficulty to sample: may hide, run away, move to quickly to count. Footprints, droppings or burrows may be easier to sample.
• Sweep netting - walk through the habitat and sweep it in wide arcs with a stout net. Small animals (such as insects) will be caught in the net. Used for water habitats or low vegetation that is not too woody.
• Pitfall trap - bury a small container with steep sides in the soil so that the rim is just below the surface. Small animals will fall into the container. Shelter the trap from the rain, so that it does not fill up.
• Tullgren funnel - device for collecting small animals from leaf litter. Place leaf litter in the funnel The light drives the animals downwards, especially as the litter dries out and warms up, where they fall through a mesh screen into the jar beneath.
• Mark and recapture technique: 1. capture a sample of animals (C1). 2. mark the animals. 3. release the animals back into their habitat. 4. after some time, capture some more animals. (c2). 5. count the number of marked animals (c3) Total population= (C1 x C2) / C3

Simpson's Index of Diversity

• A high value indicates a very diverse habitat - lots of different species and lots of organisms.
• One species doesn't dominate the others, so if there is a small change to the environment, the habitat is stable and able to withstand change
• A low value indicates the habitat isn't very diverse and is dominated by a few species.
• A small change to the environment could damage the whole habitat because if one of the dominating species is affected, the whole habitat is likely to change.
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Measuring genetic diversity

• Genetic diversity is calculated for isolated populations, such as in zoos & captive breeding, rare breeds and pedigree animals, to measure the value of that population as a resource for conservation.
• Genetic diversity can be seen if there is lots of variation in a visible feature, such as hair colour, size and eye colour.
• Genetic diversity is found where there is more than one allele for a particular locus. This will mean that there are more genetic differences between the gametes.
• Genetic diversity can be calculated by proportion of polymorphic gene loci (a locus that has more than two alleles.) Having more than 2 alleles at a locus increases genetic diversity. An example of polymorphic gene locus is the ABO blood grouping.
• Proportion of polymorphic gene loci = number of polymorphic gene loci / total number of loci.

Factors affecting biodiversity

• Human population growth: greater demand for food, consumer goods and space, harming other species and habitats which may lead to extinction. Pollution, altering ecosystems to suit ourselves, destroy and fragment habitats and use more of Earth's resources are all ways in which human population growth affects biodiversity.
• Agriculture: clearing natural vegetation destroys habitats and population size of wild species, leading to reduced biodiversity leaving species with less capacity tot adapt to change in their environment. Modern agriculture relies on monoculture (a crop consisting of one strain of species) and selective breeding (selecting particular traits to breed - reduces genetic diversity). leading to genetic erosion (reduced genetic diversity of a species.)
• Climate change: significant, long-lasting changes in weather patterns. Loss of genetic diversity means species are less able to adapt to the changing climate. Instead, they migrate to follow the weather patterns they are suited to leading to a slow migration of populations and ecosystems towards the poles. Major human development, agriculture land, large bodies of water and mountain ranges are all obstructions to this migration. Selectively breed agricultural species are unlikely to adapt so food production will decline.

Reasons for maintaining biodiversity

• Ecological:
• interdependence of organisms - all organisms in a habitat are interlinked by a food web. When one species is affected by human activity, other species will be affected too. A habitat with greater species diversity tends to be more stable and able to withstand some change. A keystone species is one which has a disproportionate effect upon its environment relative to its abundance. A decline in a keystone species will have a dramatic effect on the habitat.
• Maintaining a genetic resource - populations of wild plants and animals have evolved adaptions to changing environments for thousands of years. Genetic diversity is needed for these adaptions to occur. These species may contain molecules that can be used as pharmacological products to combat disease
• Economic:
• Natural ecosystems perform processes that are valuable to humans, including regulation of atmosphere and climate, purification and retention of fresh water, fertilisation of soil, recycling nutrients, detoxification and recycling wastes, crop pollination, growth of timber, fuel and food, discovery of potential molecules for medicines.
• Soil depletion is the most immediate effect lack of biodiversity has - continuous monoculture takes minerals out of the soil and not returned because the crop is harvested
• Aesthetic:
• Natural systems are good for our physical, emotional and intellectual health and wellbeing
• Reduced biodiversity increases chance of flooding

Conservation in situ

• Conservation in situ - carrying out active management to maintain the diversity in the natural environment
• Pros: species conserved in the natural environment, protects biodiversity, natural & culture heritage, facilitates scientific research
• Cons: endangered species may become fragmented, population may have lost genetic diversity already, conditions that caused the habitat to become endangered may still be present, could act as a 'honeypot' for poachers and tourists
• Legislation - stop activities such as hunting, logging and clearing land for agriculture. Can be difficult to persuade legalislation is needed and difficult to enforce.
• Wildlife reserves - areas set aside for the conservation of species or habitats. Needs to be large enough and big enough diversity to provide for the long-term survival of all species and populations represented. Should meet the needs of the indigenous people. Problems include: protected animals coming out of the reserve to raid crops, continued poaching, illegal harvesting and tourists disturbing the environment
• Marine conservation zones - areas of the sea set aside to conserve the diversity of species and habitats

Conservation ex situ

• Conservation ex situ - conservation outside the normal habitat of a species
• Pros: protected from poaching and predators, health can be managed, genetic diversity can be measured and selective breeding to increase it can be done, research is easier, can be used as attractions to raise funds for further conservation, education
• Cons: limited genetic diversity, exposed to a wide range of diseases, animals may not behave normally & nutrition can be hard to manage, correct environmental conditions can be difficult to achieve, if reintroduced may have difficulties fitting back into natural habitat
• Zoos - sites which focus on breeding endangered species and conducting research which will benefit them, which the public can visit. Modern reproductive techniques can be used to help with genetic diversity.
• Botanic gardens - conservation of plants ex situ which the public can visit. Seeds can be collected from the wild without too much disturbance and stored & germinated in protected surroundings. Can be bred in large quanities for research & reintroduction to the wild. Funding can be difficult, genetic diversity will be limited and research conclusions may not be representative for the whole species
• Seed banks - collection of seed samples which store rare and useful seeds, kept in very dry and freezing conditions. Seeds remain viable for decades. Can provide food crops and building materials. Seeds need to be tested periodically to ensure they are still viable.

Conservation agreements

• CITES - the Convention on International Trade in Endangered Species of Wild Fauna and Flora - international agreement between most governments in the world, first made in 1973. Main aim: to ensure international trade in specimens of wildlife does not threaten their survival. To do this it: regulates and monitors international trade in selected species, trade in wild plants for commercial purposes is banned, trade in artificially propigated plants is allowed with a permit, less endangered species may be traded with a permit
• Rio Convention on Biological Diversity - signed by 150 government leaders at 1992 Rio Earth Summit. Main aim: to promote sustainable development. Aims: conservation of biological diversity, sustainable use, shared access to genetic resources, scientific knowledge and technologies and its benefits
• Countryside Stewardship Scheme (a local conservation scheme) - introduced in England in 1991. Payments were made to farmers & land managers to enhance and conserve English landscapes. Grants available for hedge laying, planting and repairing dry stone walls. Aims: improve natural beauty and diversity, enhance & restore landscapes, their habitats and historical features, improve opportunities for public access. Replaced by Environmental Stewardship Scheme in 2005.