Biodiversity (AQA A Level Geography)

Biodiversity is defined by the Convention on Biological  Diversity (1992), as ‘the variability among living organisms from all sources including terrestrial, marine and other aquatic ecosystems and the ecological complexes of which they are a part; this includes diversity within species, between species and of ecosystems.’ 

• In other words, biodiversity is the amount and assortment of biological life forms; that are found in a particular area; and its changes over time
• It includes variety within, and between, species and ecosystems
• Ecosystems are communities of living organisms (biotic - plants and animals), sharing the environment, with the non-living (abiotic - light, water, soil etc.) components
  • Each ecosystem is unique at a local level
  • Biodiversity varies on a local scale:
    • Natural habitats will have higher biodiversity than agricultural land
• Biomes are very large ecosystems on a global scale; such as tropical rainforests, savannahs, deserts etc. 
  • Each biome share similarities but differ at the local level
  • Tropical rainforests share general features such as climate and overall appearance 
  • However, each tropical rainforest's biodiversity will differ, along with its composition and interactions
• Ecosystems are dynamic systems and develop through distinct succession from a 'sterile' area to a climatic climax community
• Plant succession affects food chains, biomass, species diversity and size of organisms

Measuring biodiversity

• Biodiversity is measured through:
  • Indicator species
    • Certain species are used as an indication of environmental conditions
    • Often used as evidence in planning and conservation of an area
  • Species richness
    • Provides a direct link between biodiversity and the number of species 
    • Measures the total number of the species in a community
    • Difficult to produce a complete inventory of all the species present in a location as living organisms are dynamic and areas change 
  • Living Planet Index (LPI)
    • This measures the state of the world's biological diversity - the health the world's ecosystems 
    • Based on average changes in the population of vertebrate species from terrestrial, freshwater and marine habitats
  • Population number
    • The amount of a genetically distinct population within a particular species
    • E.g. Butterflies as a species, but Red Admiral as a genetically distinct population 
  • Evenness indices
    • Shows how evenly spread individuals are in a community of different species
  • Genetic diversity
    • This is the total amount genetically different information found within a species 
    • Genetic differences allow species to adapt to its changing environment
    • Also known as natural selection

Distribution of biodiversity

• Biodiversity is not equally distributed within ecosystems or biomes
• Biodiversity decreases further away from the equator (north and south)
• Approximately 50% of global biodiversity lives within tropical rainforests
• This is due to the climate being wetter, warmer, with little seasonal variation; making it a reasonably stable climate that supports continuous plant growth
• Which, in turn, supports greater biodiversity along the food chain

Global scale

• Overall biodiversity is declining at both local and global levels
• Very few global ecosystems are untouched by human activity
• Extinction rates have increased a 100 fold compared to natural background extinction rates
• Scientists believe we are in a 6th period of mass extinction - due to human activity
• Biomes with the highest rates of degradation are tropical, temperate, flooded grasslands/savannahs and tropical deciduous forests (aka monsoon forests or tropical dry forests)
• The WWF's Living Planet Index (LPI), shows a general decline of the world's biodiversity:
  •  1970 - 2002 approx. 40% 
  • The decline rose to 58% by 2012
  • The latest report shows a 69% decline of the world's biodiversity from 1970 - 2018
  • Freshwater populations have been hit the hardest with an average decline of 83% since 1970

Biodiversity Decline by Region in Descending Order

Region	Percentage	Species Hardest Hit
Latin America and the Caribbean	94%	Freshwater fish, reptiles and amphibians
Africa	66%	Freshwater fish and mammals
Asia and Pacific	55%	All groups
North America	20%	Overall decline but also shows signs of stabilising
Europe and Central Asia	18%	Amphibian, reptile and freshwater fish, although shows signs of stabilising

Local scale

• The UK’s National Ecosystem Assessment (NEA, published in 2011) presented a thorough account of the ecosystem services provided by biodiversity that are essential for national social and economic wellbeing
• The NEA showed the value of biodiversity to the UK, for example; 
  • The value of inland wetlands for water quality
  • The value of pollination to agriculture
• The UK also has habitats and species of global significance:
  • Approximately 13% of the world’s blanket bog
  • 20% of Europe’s lowland heathland
  • Important collections of mosses, liverworts and lichens
  • The UK’s estuaries are a crucial migratory links for waders and wildfowl

Blanket bog 

• These bogs are extensive and widespread in the wetter, flat or gently sloping uplands of west and north UK
• Found from 1000m down to sea level on poor draining ground with a peat level of at least 0.5m 
• Development began during warmer and wetter climates in the UK and further aided through forest clearance which increased waterlogging
• Heathers, bog mosses, and cotton grasses have adapted to survive on the acidic and infertile ground
• Dwarf shrubs appear in the more drier, eastly regions 
• With higher altitudes allowing mountain crowberry, bearberry and bog bilberry to grow
• Purple moorland grass is dominant on the steeper westerly slopes

Human activity on blanket bogs

• Industrial peat extraction destroyed many bogs and tax incentives during the 1980s saw afforestation of vast areas 
• Drainage resulted in shallow drains being dug across peatlands and over-grazing by livestock
• Burning to promote fresh growth for grazing or bird nesting has led to the loss of peat forming mosses, along with shrinkage, desiccation and erosion
• Climate change will lead to temperature increases and rainfall variations, which will all impact on the biodiversity of the bogs, although the extent of the change is difficult to evaluate

Changes to a Bog Blanket's Biodiversity in the UK

Cause	Consequences	Impacts
Increased temperatures	Longer growing season	Loss of niche vegetation Increase in invasive bracken at higher altitudes Increase in nitrogen deposits and carbon sequestration
Hotter and drier summers	Increased evapotranspiration and lowering of water table Drought Wildfires	Change in dominant species Increased wind erosion of exposed peat Changes in agricultural potential and habitat of ground nesting birds
Wetter winters	Increased overland flows and increased rainfall intensities	Gully erosion Peat stability is lost Increased land slides
Longer grazing period	Over-grazing	Biodiversity decline
Access by walkers, ramblers and hikers	Footpath erosion Damage to stabilising vegetation Littering	Peat loss Exposed peat areas subject to drying out, wind and gully erosion  Increased pollution and damage to wildlife
Wildfires	Peat is lost and burning can continue underground for miles	Loss of biodiversity and release of carbon into the atmosphere increasing global warming
Drainage of peat bog	Water table is lowered	Change of dominant plant species Allows access to invasive plant species Habitats are lost or changed

Recent trends

• Whilst the trend of biodiversity loss is downwards, it is showing signs of slowing
• This is due in part to:
  • Introduction of green spaces in urban areas
  • Farmers rewilding and planting hedges
  • International polices on the trade of plants and animals 
  • Education on the value of biodiversity 
  • Adoption of polices to manage invasive alien species - bio-hazard controls
  • Designation of protected areas - conservation and national parks and sites of special scientific importance etc. 
  • Regulations to support sustainable harvesting, reduction of pollution and habitat restoration
  • Policies to protect individual species or particular ecosystems 
  • New building regulations that include environmental analysis 
  • Increased recognition of local and indigenous knowledge and community managed areas

• Any decline in biodiversity negatively affects global well-being

Causes and Impacts of Biodiversity Decline

Causes	Impacts
Exploitation via hunting, harvesting and fishing	Reduces the habitat and population of species
Habitat degradation, change or loss	Deforestation to make way for agriculture, change of soil nutrients, loss of carbon sequestration  and release of CO2 into the atmosphere
Urban development	Changed land use, loss of habitats and biodiversity, increased CO2 production and changes in river drainage and availability of fresh water. Biological waste material increases further contributing to atmospheric pollution
Energy production	Fossil fuel combustion increases atmospheric CO2
Pollution	Damage to habitats and species through run-off from agricultural chemicals and industrial processes
Climate change and global warming	Rising sea levels and changes to abundance and distribution of species. Industrial farming of cattle increases atmospheric methane
Mobility/globalisation	Movement of people have transported organisms across geographical barriers - some can be beneficial others are invasive and destructive (introduction of grey squirrels into the UK or Dutch Elm Disease accidentally imported into the UK from Canada in the late 1960s

• Impacts of biodiversity loss can be viewed as physical or human 

Categorising Biodiversity Decline into Physical and Human Impacts

Physical	Human
Loss of one species may result in the extinction of dependent species	Reduction in food supplies through a loss of pollinating insects and birds carrying seeds
Fewer plants reduces CO2 uptake and increases greenhouse effect in the atmosphere	Air quality and water purity declines through declining biodiversity which will impact human health
Loss of vegetation affects the water cycle leading to floods or droughts	Potential sources of medicines are lost
Bare, exposed soil is vulnerable to erosion, leaving land infertile for growth of crops	Loss of crops through erosion can lead to famine

• Overall, biodiversity loss impacts vulnerability to natural disasters, increases energy and food insecurity, and decreases access to raw materials and potable water