Biodiversity refers to the variety of living organisms in an area. It can be considered on three levels:
1. Habitat diversity - number of different habitats in an area (the area inhabited by a species including the physical factors such as soil and temperature range, and the living factors like the availability of food and presence of predators).
2. Species diversity - number of different species and abundance of each species in an area (group of similar organisms able to reproduce to give fertile offspring).
3. Genetic diversity - variation of alleles within a species or a population of a species (versions of a gene).
Collecting data on biodiversity involves finding out the number of different species in a habitat or the number of individuals in each species.
Samples are taken because individual counting would be too time-consuming.
- Choose an area to sample (should be random to avoid bias and ensure sample is representative) - grid and random number/letter generator technique
- Random sampling - every individual has the same chance of being sampled
- Record number of different species or count number of individuals of each species
- Plants - quadrat
- Ground insects - pitfall trap
- Flying insects - sweepnet
- Aquatic animals - net
- Repeat process, take as many samples as possible, calculating mean will make estimate more reliable
- Use same sampling technique for other habitats when comparing
Species Richness/Evenness and the SID
Species richness is the number of different species in an area. Higher number of species = greater species richness.
Species evenness is the measure of the relative abundance of each species in an area. More similar population size of each species = greater the species evenness.
Greater species richness and evenness in an area = higher the biodiversity.
Simpson's Index of Diversity measures species diversity by taking into account species richness and species evenness.
The result is always a value of 0 to 1 where 1 is the most diverse habitat possible.
High index values suggest the habitat is more capable of coping with change, whereas low index values suggest the habitat is more easily damaged by change making it less reliable.
Global biodiversity is the total number of species on Earth including:
- Named species - between 1.5 to 1.75 million species, not exact because no central database, different opinions about classification of some species
- Unnamed species - large proportion of species not yet named on Earth, many undiscovered or not yet named
Estimates for total number of species on Earth ranges from about 5 to 100 million, recent estimates 14 million:
- Different techniques to estimate
- Little known about some groups of organisms
- Biodiversity varies in different part of the world, many areas largely unexplored
- Estimates change as new things found
Climate change occurs naturally but current climate change is being accelerated by humans increasing emissions of greenhouse gases, which causes global warming.
1. Changing environmental conditions can increase or decrease biodiversity
- Some areas will get colder, some warmer, some wetter, others drier
- Most species need particular climate to survive, so previously inhabitable areas may become uninhabitable and vice versa
- This could increase/decrease range of some species
- Some species forced to migrate to more suitable area, changing species distribution
- If no other suitable place, or species cannot migrate or if change too fast, species may become extinct
2. Spread of disease can increase or decrease biodiversity
- Ranges of some disease-carrying insects may increase
- Change in distribution
- Warmer and wetter conditions can encourage spread of fungal diseases
3. Changing agricultural patterns
- Changes in temperature, rainfall, season timings, flood frequency and drought
- Land previously unsuitable can become available for agriculture and vice versa
- Different crops grown can disrupt food chains
- Extreme weather may cause crop failure and disrupt food chains
Importance of Biodiversity
- Products from animals and plants traded on local and global scale
- Food and drink
- Clothing (fibres and fabrics) e.g. cotton from plants, leather from animals
- Drugs (plant compounds) e.g. morphine from poppies
- Fuels (renewable fuels) e.g. ethanol, biogas
- Industrial materials e.g. wood, paper, dyes, adhesives, oils, rubber, chemicals
- Conserve currently used organisms as well as not currently used organisms, may provide new products in the future
- Complex relationships between organisms and their environments
- Food chain disruption
- Nutrient cycle disruption e.g. decomposers improve quality of soil
- Habitat loss e.g. hedgerows are wildlife corridors, safe movement between different habitats, nesting sites, isolation, food availability
- Climate change e.g. CO2 stored in trees and bogs
Importance of Biodiversity (cont.)
- Right thing to do to conserve species
- Right to exist, shouldn't become extinct as a result of our activities
- Moral responsibility to conserve biodiversity for future generations
- Religious and spiritual reasons - to be at harmony with the natural world
- Brings joy to people, pleasant and attractive environments
- More visitors - more economic advantages
- Pollinators to pollinate crops
- Protection against disasters - risk of losing food supplies if only one or two species used
- Source of food
- New varieties for cross-breeding to improve characteristics, cope with climate change
- Pest control
Conservation can help maintain biodiversity by protecting and managing species and habitats. It is important to ensure the survival of endangered species or threatened habitats. Critically-endangered species are likely to become extinct because their population size is too small.
1. In situ
- On site conservation - protecting species in their natural habitat
- Establishing protected areas e.g. national parks and nature reserves where urban, industrial development and farming are restricted
- Controlling/preventing introduction of species that threaten loclal biodiversity
- Protecting habitats e.g. coppicing, controlling water levels to maintain wetlands
- Restoring damaged areas
- Promoting particular species by protecting food sources and nesting sites
- Legal protection
Adv - both species and habitats conserved, larger populations protected, less disruptive, greater chance of recovery
Disadv - difficult to control some threatening factors e.g. poaching, predators, climate change
2. Ex situ
- Off site conservation - protecting species by removing part of the population from a threatened habitat and moving them into a new location
- Relocation to a safer area
- Breeding in captivity (zoos, animal sanctaries) then reintroducing to the wild
- Botanic gardens as controlled environments to grow variety of rare plants for conservation, research, display and education, then reintroduced to suitable habitats
- Seed banks where seeds can be frozen and stored for over a century without losing fertility, good back-up source for natural reserves
Adv - protect individual animals in controlled environments, predation and hunting can be managed, reduced competition for resources, check health and treat for diseases, manipulated breeding, reintroduction
Disadv - only small number of individuals can be cared for, difficult and expensive to create and sustain right environment, less successful, difficulty breeding in captivity, difficult to adapt to new location
Environmental Impact Assessment
- an assessment of the impact a development project might have on the environment
- estimating biodiversity on project site, evaluating how development might affect biodiversity
- identify ways biodiversity can be conserved, threatened/endangered species on project site and laws regarding their conservation
- Used in deciding planning stipulations e.g. relocating/protecting endangered species
- Conservation more likely to be successful if countries work together
- Information about threats to biodiversity should be shared and countries decide on conservation methods and implement them together
- Rio Convention on Biodiversity - international agreement that aims to develop international strategies on biodiversity conservation and how to use animal and plant resources sustainably, international law that conserving biodiversity is everyone's responsibility, guidance on how to conserve biodiversity for governments
- Convention on International Trade in Endangered Species (CITES) is an agreement designed to increase international cooperation in regulating trade in wild animals and plants, all member countries illegal to kill endangered species, conserve species by limiting trade through licensing, illegal to trade products made from endangered animals, raise awareness of threats to biodiversity through education