Biodiversity - Genetic diversity, species diversity & ecosystem diversity
Genetic diversity: the range of species found within a particular species. Genetic diversity often determines the degree of resistance to pests & diseases.
Species diversity: the variety of plant & animal species present in an ecosystem. Diversity is needed to enable the ecosystem to carry out its functions, such as carbon cycling, with maximum efficiency. Species diversity supports an ecosystem's resilience to withstand climate change. Removing species from the various trophic levels can have a huge impact on energy flows & nutrient cycling. Species diversity also includes the rarity of some of the constituent species (endemism).
Ecosystem diversity: the number of different ecosystems within a given area. This is partly controlled by physical conditions, particularly climate, geology, relief & soils. The ability of people to modify & eliminate ecosystems is a threat to ecosystem diversity.
Biosphere - the thin veneer of living material on the planet's surface
Biome - a global scale ecosystem e.g. a tropical forest
Biomass - the total weight of living matter per unit area (dry)
Processes & Factors Influencing Biodiversity
Numerous factors influence biodiversity, some on a global scale, others on a regional or local scale. Both physical & human factors are important.
Global & continental factors: primary ecological factors determine the broad framework within which other ecological factors operate.
- Size of area: overall biodiversity increases with area, large continuous biomes support a wider range of species & extensive boundaries encourage migration.
- History & age: generally biodiversity is greatest in the oldest & least disturbed ecosystems, especially in the tropics, where there are few physical constraints on productivity.
- Isolation: geographical isolation, particularly on remote islands, reduces the number of species but encourages endemism, as the remaining species develop in a distinctive way e.g. in the Galapagos islands.
- Altitudinal range: a large altitudinal range means a cross-section of diff. climates. The more climatic zones involved, the more diverse the habitats are. Same principle applies to ocean depths.
- Productivity: V. significant factor - high temps & humidity levels, rich supplies of nutrients, light for photosynthesis & a lack of annual seasons encourage high primary productivity& therefore abundant energy e.g. in rainforests & coral reefs.
-Habitat architecture: high primary productivity encourages the development of a complex trophic pyramid with many ecological niches. Capable of supporting high levels of biodiversity.
Processes & Factors Influencing Biodiversity (2)
- Succession: biodiversity increases as species establish themselves, interact & subtly alter the environment.
- Interaction between species: can lead to competition which in turn may drive certain species to extinction, particularly when exotic species are introduced.
- Disturbance: major environmental disasters such as fires, flooding & storms can destroy biodiversity.
- Dispersal & colonisation: individual species dispersal & colonisation rates have an impact on biodiversity.
- Changes in local land use & cover
- Species introduction/ removal
- Technology adaptation & use
- External inputs (fertiliser use, pest control & irrigation)
- Harvest & resource consumption
- Climate change
- Cultural & religious uses of land
Natural Influences on Biodiversity - simplified
- Altitude produces a range of ecological zones, each with its own species - low altitude (close to equator) promotes growth
- Lack of factors to limit growth: lots of light, warmth & rain - lots of primary productivity (southern hemisphere, mountains, rainforests)
- Decay & nutrient cycling are rapid in tropical soils - creates biomass
- Large areas can support large numbers of species in complex food chains
- Islands are isolated, so evolution goes its own way producing new unique species & varieties; endemism.
Hotspots - Norman Myers
- High species richness
- High levels of endemism
- Facing severe human threats
Combined area covers just 2.3% of the Earth's land surface. Each hotspot has already lost at least 70% of its natural vegetation. Over 50% of the world's plant species & 42% of all terrestrial vertebrate species are endemic to the 34 biodiversity hotspots.
- All terrestrial - originally marine ecosystems ignored
- Located in MEDCs - more money
- Bias towards tropical ecosystems - no tundra-ecosystems
- Iconic species protected/ key-stone species often ignored
Value of Ecosystems
Provisioning services (goods): products derived directly from the ecosystem, e.g. timber for fuel, or fruits, meat & fish for food. Some are sustainable e.g. fruits & nuts, but exploration as good such as timber can exhaust the supply.
Regulating services: those which are vital to Earth's systems e.g. forests act as the 'green lungs' of the world - important carbon sinks. Also protect against flooding & soil erosion on slopes, provide water purification & disease regulation.
Cultural services: aesthetic & spiritual enjoyment, educational value, recreation & leisure.
Supporting services: processes such as nutrient cycling, soil formation & primary production that are vital to well-being of ecosystem itself plus includes the provision of wildlife habitats. Not services that support people.
The World Resources Institute (WRI) has identified factors that threaten biodiversity:
- An unsustainable high rate of human population growth & natural resources consumption
- Inequality in the ownership, management & flow of benefits which threatens the livelihoods of the world's poorest people
- The concentration of agriculture, forestry & fishing on a narrowing spectrum of products
- Economic systems developed by governments & businesses that fail to value the environment & its resources
- Legal & institutional systems that promote unsustainable exploitation at the expense of more sustainable strategies
- Lack of knowledge & understanding in the management & conservation of biodiversity
- Localised deforestation; clearance for farming & urbanisation
- Tourism development; trampling, erosion; urbanisation & associated pollution; increased risk of wildfires; sewage, eutrophication
- Overfishing & harmful forms of fishing (dynamite & cyanide)
- Run-off from farms & urban areas; eutrophication & heavy metals in rivers, lakes & seas
- Mining, ranching & overgrazing, road building leading to ecosystem fragmentation
Biodiversity Threats (2)
Global threats: Global warming: Rising sea levels (threaten coastal ecosystems - coral, mangroves), rising ocean temps (threaten coral through bleaching), shifts in climate zones (will stress biomes; migration patterns will be altered; some biomes (tundra, montane forest) may be wiped out.
Desertification: A widespread & complex problem; some 10-20% of dryland ecosystems are already degraded; grasslands are V. vulnerable. Overgrazing, climate change, poor farming practice & population pressure all contribute. Once soil is eroded, ecosystem recovery is V. difficult. Disrupts nutrient cycle.
Poverty & food insecurity: Population pressure, poverty & the need to produce food are leading to unsustainable use of ecosystems worldwide. overfishing, deforestation, conversion of ecosystems into farmland are all major causes of ecosystem & biodiversity loss.
The Stern Review on the economics of climate change (2005) argues that climate change is likely to occur too rapidly for many species to adapt. Species have been moving polewards by an average of 6 km per decade. Phenological studies show that seasonal events such as flowering & egg laying have been advancing by several days each decade. Coral bleaching resulting from warming oceans has increased since the 1980s. This combined with ocean acidification caused by rising sea levels of carbon dioxide in the oceans, poses a threat to the well-being of many coral reefs. The degree to which biodiversity is threatened by climate change will depend on the scale & rate of incr. in global temps. A temperature rise of 2 degrees could lead to 15-40% of land species facing extinction, whilst an incr. of 3 degrees could leave 20-50% of terrestrial species facing extinction. Also at this temp, mangroves will be flooded, removing a natural coastal defence. Coral reefs will die. Strong drying in the tropics could lead to destruction of rainforests.
Disruption of Ecosystem Processes
- Energy flows: Primary producers (green plants) at trophic level 1 convert sunlight into energy by photosynthesis. As energy is lost through respiration at each stage of the process, the amount of biomass at each trophic level decreases. A food chain, or more usually a more complex food web, exists between the trophic levels.
- Nutrient cycling: the circulation of chemical elements from the environment to organisms & back to the environment. Nutrients are stored in 3 parts of the ecosystem: in the soil, the living biomass & in surface litter - they cycle between them via 3 main pathways. In the uptake or growth pathways, compounds of nitrogen, phosphorous, potassium etc are taken from the soil by plants. As plants or animals die, they contribute nutrients to the litter store via the fallout pathway. The decay pathway is formed by decomposition of litter to humus. People can have an impact on the cycle by adding nutrients via fertilisers, by reducing the biomass through over-harvesting & deforestation, & by degrading the soil. Once deprived of nutrients, soils are vulnerable to erosion.
Alien Invasive Species
- Species that move out of their natural habitat & colonise new areas; often through human activity - some deliberately moved (food sources, predators or ornamental species) or accidental introductions.
- Successful invaders tend to be: Capable of rapid reproduction, able to disperse, rapid growing, tolerate a range of environmental conditions & able to eat a wide range of foods.
- Successful species: rats, goats & the Chinese Mitten crab.
- Alien species lack native predators.
- Some species arrive by ship e.g. the zebra mussel arrived in North America from the Caspian Sea in the ships' ballast water or possibly clinging to the sides of ships. In the absence of predators they multiplied in Lake Erie to 70,000 per square metre & reduced phytoplankton by 80%.
Has a significant impact on ecosystem processes. Excess nutrients in the soil, usually in the form of nitrates & phosphates, are washed into lake & rivers. This is a natural process, but it has been increased by human activity, particularly the use of chemical fertilisers & detergents, the release of farmyard slurry & the removal of hedgerows, which causes increased soil erosion. Many lakes are now overloaded with nutrients. The result of nutrient loading is eutrophication. Initially, the extra nutrients reaching ponds & lakes lead to increased growth of water plants. Microscopic plants proliferate, causing algal blooms - these block out light in the lower depths, reducing the number of larger plants. Zooplankton are primary consumers & feed on the algae, but as the large plants die, fish take to eating more & more of the zooplankton. Algae consumptions declines. Dead algae pile up & are gradually broken down by bacteria, but this uses up oxygen in the water. Falling oxygen levels lead to the death of both plants & animals, causing the food chain to collapse & the pond/ lake to become almost lifeless. This process is happening in over three-quarters of the world's lakes. Eutrophication can also have numerous knock-on effects including contaminated drinking water.
Sustainable yield: The 'safe' level of harvest that can be hunted/ caught/ utilised without harming the individual ecosystem.
- Maximum sustainable yield (MSY): the greatest harvest that can be taken indefinitely while leaving the ecosystem intact. Over-harvesting or overexploitation tend to be the result of commercial rather than subsistence activity.
- Optimum sustainable yield (OSY): the best compromise achievable in the light of all the economic & social considerations. This level of yield, unlike the MSY, will not destroy the aesthetic or recreational value of the ecosystem & will therefore allow multiple use for the maximum benefit to the community.
- Carrying capacity: the maxim human population that can exist in equilibrium with the available resources.
Key Players in Ecosystem Management
- Scientists & Researchers
- International Organisations
- National governments operating globally & internationally
- Local & regional governments
- Artists & Poets
- Local communities including indigenous peoples & farmers
- Consumer & special interest groups
- Transnational & private enterprise
IGOs: Different arms of the UN are responsible for CITES (convention on international trade in endangered species) & World Heritage Sites. Scientific research & monitoring are important aspects of their work. Behind 2010 year of biodiversity.
NGOs: Greenpeace campaign to keep issues in the media & lobby governments.
Governments: Implement & police treaties like CITES, plus set up & run National Parks & other conservation areas.
In the 1960s, total protection was very popular, with area completely fenced off from local people. However in the 1980s concepts such as biosphere reserves surrounded by buffer zones for use by local people were developed. In the 21st C, conservation means much more than guarding rare species inside fenced, scientific reserves. Economic development is integrated with biodiversity conservation, using a huge variety of sustainable strategies, all adapted to suit the particular habitat & involve local people. Total protection strategies have been criticised for a no. of reason, although they're still used:
- In the poorest countries, there is a conflict between conservation & cutting people off from biodiversity
- Totally protected reserves are often narrowly focused for scientific purposes, & there may be a failure to see that conservation is also influenced by social, economical, cultural & political factors
- Many protection schemes were based on political & administrative boundaries, whereas ecosystems are defined by natural borders
- Protection strategies often rely on coordination by outside agencies which are not always alert to the needs of the local people
Today, much more attention is given to the design & distribution of reserves. There is also discussion about conservation priorities - many argue conservation should target the hotspots as these contain maximum diversity or endemism & are under the greatest threat. In contrast, WWF favours a broader approach in which representative areas of land & sea known as ecoregions are targeted to save a maximum variety of habitats & species. Still others argue that conservation should be focused on developing countries because the costs are lower & there is greater chance of getting value for money. High-profile & iconic species such as whales, tigers & pandas tend to attract more interest & therefore funding, but this is questioned by some groups as keystone species such as bees are crucial but hard to 'sell' to a wary public.
Restoration & Conservation
Restoration of highly degraded ecosystems is the ultimate conservation challenge. It can include recreating wetlands (river restoration) or linking up small fragmented reserves to produce a larger, more climate-proof reserve e.g. the Great Fen project in East Anglia. These reconnection schemes require costly land purchases, so they have to emphasis local benefits such as recreation. Restoration of derelict sites such as spoil heaps, mines & quarries is even more expensive because the ecosystem & habitat have to be reconstructed virtually from scratch.
Conservation: An alternative to in-situ conservation is for endangered species to establish a captive population away from its natural habitat (ex situ conservation). This includes captive breeding with release schemes, & biodiversity banks such as genetic & seed banks in zoos & botanic gardens. Several species have been saved in this way including the giant panda. Ex situ & in situ conservation work together to incr. endangered populations & re-establish near-extinct ones.
Conservation aims: Conserve & improve hydrological systems, prevents & control erosion & sediment, conserve & improve timber & related forest resources, habitat conservation, protect wildlife resources, conserve genetic resources, provide opportunities for recreation, provide opportunities for research, monitoring & education, support lifestyles of indigenous people & control exploitation of resources.
- Only 12% of the Earth's land surface is designated as receiving some sort of protection. Less than 1% of marine areas are currently protected
- Protected areas are unevenly distributed
- There is a shortage of funding for protection & conservation
- The fact that an area is declared 'protected' does not guarantee successful conservation. 'paper parks'
- Protecting vast, remote areas from illegal human activity such as poaching is a challenge
- Outside protected areas, biodiversity continues to be threatened by pollution, climate change, invasive species & unsustainable development
Scenarios: there have been several attempts to explore plausible futures for ecosystems & human wellbeing. WWF anticipates 4 scenarios:
Business as usual: leads to increased ecological footprint & no reduction in the 'overshoot' (the amount by which the ecological footprint exceeds the biological capacity of the space available to that population).
Slow shift: gradually reducing the ecological footprint by developing many sustainable policies so that biological capacities recover by the year 2100.
Rapid reduction: with radical policies to control ecological footprints, leading to elimination of the overshoot by 2040.
Shrink & share: breaking down the world into regions in order to share responsibility.
Biodiversity Futures (2)
UNEPs GEO-4 Project (2007) also identifies 4 possible futures for biodiversity & ecosystems:
Markets first: Profit driven future, playing lip-service to sustainability. Continued degradation of biodiversity.
Security first: 'Me-first' - the focus is on maintaining the wealth of the few in a very unequal world; IGOs like the UN are viewed with suspicion; the environment is there to be exploited.
Policy first: A greater balance between human & ecological wellbeing, but humans are put first & ecosystems are protected when possibly & expedient.
Sustainability first: Equal weight is given to human & ecological wellbeing, & thinking is long-term to gradually recover lost ecological ground.
Economists think in terms of 5yrs, conservationists think it terms of 1000s of yrs.
The Impacts of Global Warming on Biodiversity in t
- Localised shifting of ecosystems in a poleward direction. Coniferous forests will expand into the tundra zone, which in turn will spread into fragmented areas of polar desert
- The tundra, with its rare Arctic plants, will shrink as rising sea levels drown coastal areas
- Increased forest fires & insect infestations are expected to ravage coniferous forests & reduce both biomass & biodiversity
- Marine life will respond to warmer sea temps & reduce ice cover. Improved food supplies will mean bigger fish stocks & the appearance of new species
- Fragile food webs could be easily damaged, leading to loss of tundra mosses & lichens that provide the main food for animals such as reindeer (caribou). Declining deer numbers will affect species than hunt them such as wolves.
The Value of Coral Reefs
- Biodiversity: although coral reefs occupy only 0.15% of marine environment, they are home to over 25% of all known marine fish. They rival rainforests in biodiversity. Although 4000 species of reef-living fish & 800 species of reef-building corals have been identified & catalogued, scientists think these are just a fraction of the total. Many species could become extinct before being discovered. 10% of the world's coral reefs were either degraded beyond recovery or totally dead in the yr 2010
- Shoreline protection: they 'buffer' coasts from wave erosion & the impact of storms at much lower costs than artificial ones defences. These natural self-repairing breakwaters will become even more critical as global warming causes sea levels to rise
- Food: local people eat fish, conch, lobsters, sea urchins & sea cucumbers from reefs. Reefs also make a major contribution to commercial fishing - globally, 20% of animal protein consumed by people comes from marine environments, with coral reefs providing 25% of the fish catch
- Medicine: algae & sponges yield bioactive compounds used by the pharmaceutical industry. Reef species support new treatments for bacterial infections, as well as some cancers, & corals are used for bone grafts
- Building materials, decorative objects, the aquarium trade (sea anemones, sea horses), education & research (shallow water & easy accessibility from shore) & tourist magnets, almost all 109 countries with reefs in their territorial waters have established tourist industries
- Around 35% of mangrove area has been lost during the last few decades of the 20th century & the World Mangrove Atlas estimated that in 2010, 1/5 of the world's mangrove ecosystems had been lost since 1980
- Mangroves supply a no. of ecological benefits - they are habitats for many species such as commercial fish & crustaceans & therefore contribute to sustaining local fish & shellfish populations. 75% of the game fish & 90% of the commercial species in South Florida are dependent on mangrove ecosystems, plus an estimated 75% of the commercially caught prawns in Queensland depend on mangroves in their life cycle
- It was proved that areas surrounded by mangroves were less damaged by the 2004 tsunami - wave energy may be reduced 75% in the waves passage through a 200m mangrove
- Mangroves are important for keeping fishery yields in coastal & offshore areas; they supply the coastal habitat with nutrients plus offer idyllic living environments for fish, shrimps, crabs
- The root systems of mangrove species absorb inorganic matters & reduce water pollution levels. They also aid the stabilisation of water capacity on soil surface & thus prevent flooding
- Mangroves contribute to supplying nutrients & oxygen to animals & plants in the ecosystem
The Galapagos Islands - A Biodiversity Hotspot Und
The Galapagos archipelagos are located in the Pacific Ocean, west of Ecuador. The volcanic islands are made up of 13 major & 6 minor islands, + many islets. 5 of the islands are inhabited by a total population of 21,000 people - increasing 8% per year, due mainly to immigration.
The islands have a high level of biodiversity as they are V. isolated - the large distance of open water means V. few mammals have made it onto the islands; those that did are very small e.g. rich rats which come onto the islands via rafts or floating vegetations.
There are no large land-predators so animals such as the tortoise have been able to evolve into giant species. The wildlife of the islands is dominated by birds, especially marine species as the distance over the sea has less effect.
Charles Darwin lives on the island for 5 weeks in 1835 & made observations from which he concluded the Theory of Evolution - natural selection/ survival of the fittest. The Galapagos islands are an important biodiversity hotspot due to the large amount of endemism.
The Galapagos Islands - A Biodiversity Hotspot Und
Alien Species – Along with the arrival of humans on the Islands came introduced species of plants and animals. Many of these, having no natural predators, show rapid growth in numbers, threatening to dominate local ecosystems.
Population Pressures – Until the late 1990s, there was no limit to immigration from mainland Ecuador and the islands experienced 8-10% growth annually. Migrants come to work in the growing tourist industry but there is a shortage of work meaning they turn to activities such as illegal fishing or poaching of animals including the Giant Tortoise (Lonesome George) in order to support their families. As the population increases, there is an increased pressure on natural resources (water, stone, agricultural land & fuel wood) whose increased use impacts the natural ecosystems.
Tourism – Numbers have increased dramatically from 1000 per year (mid ‘60s) to 70,000+ (late ‘90s). 50% of tourists are from mainland Ecuador and there is continued pressure for luxury hotels. The result is evidence of increasing erosion of footpaths in certain areas (e.g. Bantoleme view point) and an increase in litter and waste that has to be cleared. Tourism has acted as a magnet for migrants from the mainland (looking for work in tourism industry). Tourism is also greatly responsible for the importation of fuel oils such as those carried by the “Jessica” (ran aground 2001).
Climate Change – Global climate change due to a rise in CO² emissions from human use of fossil fuels – seems to be corresponding increase in no. of El Nino events. These alter the currents around the Islands and the availability of nutrients to the food chain and have a disastrous knock-on effect on wildlife.
The Galapagos Islands - A Biodiversity Hotspot Und
Illegal Fishing – Growing problem with local small-scale fishermen (800+) and large commercial companies illegally fishing within the Galapagos Marine Reserve. Commercial boats have a huge impact on dolphin deaths in the region; usually caught as a by catch in the tuna fishery. (June 2002 – a Colombian vessel was stopped from fishing illegally & 50 dead dolphins were found within its nets; nets can be as long as 40km long, fines are very small, Captain of this vessel fined just 4 cents!). Since 1997, there has been a commercial fishing ban within the Marine Reserve but it is difficult to patrol. Smaller-scale fishermen are being tempted by non-traditional marine resources such as seacucumbers and spiny lobsters (profitable market in Asia for such products). As more fish are being taken out of the ecosystem, there will be a knock on effect throughout the food chain and eventually the unique creatures of the Galapagos may become extinct.
Oil Spills – Jan 2001, the cargo ship “Jessica” ran aground off the island of San Cristoal whilst carrying 240,000 gallons of fuel oil (great deal of aid; event made public aware of uniqueness of the Islands and its World Heritage status).
The Galapagos Islands - A Biodiversity Hotspot Und
Islands have range of levels of Protection – The National Park & the Marine Reserve are under control of the government of Ecuador but because of global importance of Galapagos they're also designated as a World Heritage Site & as a World Biosphere Reserve - gives them international protection.
Tourism – All visitors have to pay an entrance fee of $100 (part goes towards costs of maintaining the Charles Darwin Research Centre, part towards training local people as guides, but main issue; most goes to the Ecuadorian National Government).
Population – The islands need to reduce their resident population so that fewer demands are made of the fragile ecosystems; the aim was to reduce it by 2% by 2004 and to maintain it at a steady but not increasing level. Migration to the Islands from the mainland has been made more difficult by imposing quotas & insisting people have a job lined up before arriving.
Fishing – The National Park has only two patrol boats & has difficulty patrolling the area of ocean. There are very strict limits around the Islands but these are constantly being breached. Long lines & purse seine nets are prohibited but commercial fishing fleets continue to break the rules & have a serious impact on the ecosystems. Sniffer dogs are now used to try & detect illegal exports of products such as shark fin. In comparison small-scale local fishing of traditional catches has a minimal impact on marine ecosystems and can be allowed to continue. The long-term aim is to attract the fishermen to work within the tourist industry as guides to the Marine Reserve & use the waters surrounding the Islands in a more sustainable way.
The Galapagos Islands - A Biodiversity Hotspot Und
Goats, Dogs & Cats – Controlled by hunting but this is difficult on hilly terrain. The alternatives oftrapping or poisoning are unsuitable as they also harm native species. The Isabela Project aims toeradicate goats in the northern part of the island so that vegetation is plentiful for the Giant Tortoises, which are under threat due to reduction of their grazing habitat.
Iguanas and Tortoises – The eggs of both are collected and incubated with the young being kept until they are of a size more able to withstand predators.
Plants – there are several projects to eradicate invasive species but it is a costly process & has to be repeated on a regular basis. There is a call for a Plant Control Unit whose task will be focused on eradication programmes of alien plant species.
Charles Darwin Research Centre – set up in the 1960s, it monitors & records populations & acts as adviser to the government and other bodies. Also important in educating visitors and inhabitants.