Biodiversity: An Introduction (book)

Biodiversity: An Introduction (book)

1. What is biodiversity?

   • variety of life
   • there are three key elements of biodiversity
     • Ecological diversity
       • Biomes --> Bioregions --> Landscapes --> Ecosystems -->Habitats --> Niches --> Populations
     • Genetic diversity
       • Populations --> Individuals --> Chromosomes --> Genes --> Nucleotides
     • Organismal diversity
       • Domains/Kingdoms --> Phyla --> Families --> Genera --> Species --> Subspecies -->Populations --> Individuals
   • no single measure of biodiversity
   • measure may influence the findings of a particular study
     • used for making decisions about conservation actions
   • species richness has become the common currency of many studies
     • it has a practical application (measurable in practice), surrogacy for many kinds of variation (greater number of species tends to mean more/greater genetic diversity, organismal diversity and ecological diversity) and wide application (unit of practical management)
     • limitations
       • definition of a species
       • not a measure of whether an assemblage of a small number of closely related species are less or more biodiverse than an equivalent sized assemblage of more distantly related species

2. Biodiversity through time

   • overall pattern of increase in biodiversity
     • however overtime more than 90% of all species that have existed have become extinct
   • increase has been caused by radiations and stabilisations
     • caused by mass extinctions of different taxonomic groups at different times
       • high continuous levels of extinction at different periods that have major disruptive effects on the patterns of development of biodiversity
         • Late Ordovician (440mya): sea levels decreased due to climatic cooling casing extinction of marine (particularly deep-water) groups and second phase caused by end of glaciation leading to rise in sea level caused extinction of shallow-water groups
         • Late Permian (250mya): low oxygen levels in oceans, sea-level rise and climatic change caused the extinction of 95% of marine species and 70% of land species
         • End-Cretaceous (65mya): Possible extraterrestrial object lead changes to the atmosphere (dust, smoke, water vapour and sulphur dioxide) and then global cooling causing extinction of dinosaurs, pterosaurs and marine reptiles
   • bulk of biodiversity is contributed only by a relatively few taxonomic groups
     • most groups aren't very diverse
   • total number of extant species has been estimated using a variety of extrapolations
     • best estimate is approx. 13.5 million species and only 1.75 million species have been described
       • these values could have large errors
     • extrapolations include canvassing experts (estimations based on experts of different species), patterns of species description (past patterns indicate future patterns), proportion of undescribed species, well-studied areas (areas of well known species numbers are representative of areas that are not) and well-studied groups

3. Mapping biodiversity

   • species-area relationship
     • as the size of the geographical area increases, the number of species it contains increases too
   • local-regional richness relationship
     • local species richness tends to be positively correlated with regional species richness
   • there is higher taxa in marine conditions than in terrestrial
     • there are terrestrial species than marine species
   • tropical regions have at least two-thirds of all extant terrestrial species
     • Neotropics contains greatest level of extant terrestrial species
     • Indo-western Pacific has greatest level of marine biodiversity
   • distribution of terrestrial biodiversity is uneven
   • proportion of endemic species tends to increase with the size of an area and with high species richness
     • number of endemics increases towards lower latitudes
   • marine and terrestrial species richness tends to increase from temperate to tropical latitudes
     • latitudinal gradients in richness have been a similar feature throughout the history of biodiversity
   • terrestrial species richness declines towards high elevations, whilst marine species richness relationship with depth is hump-shaped
   • correlations between the number of species in different groups are often weak

4. Does biodiversity matter?

   • direct-use values of biodiversity are concerned with the consumption or production of marketable commodities
     • food
     • medicine
     • use in biological control (controlling pests, disease vectors like mosquitoes and invasive species)
     • industrial raw material (e.g. wood, fibres, dyes and oils)
     • recreational harvesting (e.g. pets, private gardens and recreational hunting)
     • ecotourism
     • many patterns of exploitation aren't sustainable
   • indirect-use values of biodiversity are more difficult to quantify
     • services provided by biodiversity which are crucial for human wellbeing (e.g. atmospheric regulation, hydrological regulation, nutrient cycling and photosynthesis)
   • ecosystem functioning increases from assemblage of very small to small numbers of species and the effect diminishes as the number of species increases further
     • higher species richness increases both species redundancy and temporal resilience of ecosystem functioning
       • increasing reliability of ecosystem functioning
   • biodiversity may also have a variety of non-use values
     • option value (future use or non-use)
     • bequest value (passing in a resource to future generations)
     • existence value (value to people regardless of use or non-use)
     • intrinsic value (inherent worth that societies, cultures or faiths give)

5. Human impacts

   • due to human activities, biodiversity loss has been taking place for a long time
     • initially associated with colonisation of some areas of the world by prehistoric people
   • since 1600, over 1000 extinctions of plant and animal species have been recorded
   • impending extinction rates are estimated to be of greater magnitude than background rates seen in fossil records
   • principal causes of biodiversity loss are direct exploitation (e.g. higher demand for bush meat and overfishing), habitat loss, degradation and fragmentation (e.g. deforestation and building settlements), effects of introduced species (e.g. competition and new diseases) and extinction cascades (extinction of one species may lead to the extinction of another)
   • ultimate causes of biodiversity loss concern the size of the human population, rate of human population growth and scale of human enterprise

6. Maintaining biodiversity

   • the Convention on Biological Diversity is one of the main global attempts to set an agenda for maintaining biodiversity
     • main objectives are the conservation of biological diversity, the sustainable use of its components, and the fair and equitable sharing of its benefits arising from the utilisation of genetic resources
     • actions have been taken but most of them are inadequate
   • not all nations will find the conservation and sustainable use of biodiversity popular
   • to know whether strategies, plans and programmes for conservation and sustainable use are appropriate and working efficiently, suitable information needs to be gathered
   • sustainable use will be integrated in national planning to minimise adverse impacts
   • conservation will require protected areas for in-situ conservation and ex-situ measures