World Wildlife Fund (1989) defined biodiversity as ”the wealth of life on earth, the millions of plants, animals, and microorganisms, the genes they contain, and the intricate ecosystems that help to build into living environment.’ Thus there are three levels of biodiversity: ecosystem, species and finer level generic diversity within species populations local and global.
The biological diversity has developed over millions of years under evolutionary pressures for each specie and ecological web to function under certain biotic and physical conditions (Zhang et al., 2010; Darwin, 1886).
For example, paleo-ecologists shown that the size of modern insects is determined by atmospheric oxygen levels and bird predations. During Carboniferous and Permian periods the insects had wingspans of up to 70cm, this is linked to hyperoxic conditions that controls the insect body size especially in flighted insects with high oxygen demand. However, oxygen was the main control only until Cretaceous period when the insects became a food source for early birds (Clapham et al., 2012).
Maintaining biodiversity richness and composition is necessary at every level for survival of species and natural communities (Boit et al., 2016). Biological diversity of species produces resources that can be used by ecosystem as well as humans, this is known as ecosystem services (Bullock et al., 2011). For example, a tropical rainforest produces wide variety of plant and animal products that are used for food, shelter and medicine. Diversity of biological communities such as wetlands, grasslands and forests also control soil composition, soil erosion, filtering of air and water (Delgado-Aguilar et al., 2017).
Financial value of biodiversity is not possible to calculate, just to put it in perspective, estimated commercial value of bees alone is $202billion/annum (Gallai et al., 2009).
Biodiversity Distribution
Figure X. Species’latitude relationship: birds in grid cells (approx611,000 km2) (Blackburn&Gaston, 2008)
Biodiversity richness increases from north and south poles towards the equator, this ecological pattern is known as Latitudinal Diversity Gradient (Sahney&Benton, 2008; Hawkins, 2001). The highest biodiversity is found in tropical regions extending from 30”north and south of the equator. This is a zone where the species rich rainforests, mangroves, coral reefs are found (Lindenmayer, 2010). In this range a less species rich habitat such as desert and savannah also found. Thus the biological diversity, clearly, cannot be dictated purely by latitude alone, but environmental conditions correlated with latitude. Over 25 drivers identified as possible causes of the Latitudinal Diversity Gradient (Gaston, 2000), some detailed in Box 2.
Knowledge Limitations
Biodiversity related data is essential for development of effective policies of land management and biodiversity conservation now and in the future (Jetz et al., 2012). Despite understandable importance, knowledge is based towards vertebrates (which make up less than 5% of Earth’s species), in the northern hemisphere, temperate regions (Gaston, 2000).
Majority of available data is available for mostly terrestrial ecosystems, with less investigations taking pace in marine or freshwater aquatic environments. An assessment of knowledge gaps was conducted by Jetz et al., (2012). It describes how much is known about global biodiversity in terms of ‘grain size’, the larger the grain the less is known about the diversity, Figure xx.
Figure xx. Grain-size and knowledge gaps in global environmental data (Jetz et al., 2012)
Community and Ecosystem diversity
Biological community is defines as species that occupy a particular location. Rainforests, deserts, coral reefs, kelp forests, heath and meadows are all can be described as biological community. Resident biological community with physical location and geology is termed an ecosystem (Beeby&Brennan, 2011).
Ecosystem exists in a cycle where all biological and physical components interact to create a cycle. The acting species in the cycle can be separated in to trophic levels.
Species diversity
Species is a set of individuals distinct from other sets of individuals, playing a distinct role in the ecosystem. It is estimated that there are 8.7million + –1.3 million species globally, with over 86% species on earth and 91% marine species still awaiting description (Mora et al., 2011). According to niche separation theory, individual species, even morphologically similar species, will have different preferences in biological or biological conditions; it is often referred to as species niche. Limited species identified and lack of ecological knowledge makes it hard to assess and protect Earth’s species richness (Rull&Vegas, 2006).
Genetic biodiversity
Genetic variation increases survival chances for a species under evolutionary pressures in a changing environment (Reusch et al., 2005), Box 5.
The necessity for assessing and conserving genetic biodiversity is recognized in scientific community and politically. United Nations developed a strategic plan to conserve biological diversity was adopted in 2011 and target N13 addresses genetic diversity conservation (Chazournes, 2000).
Understanding structure and genetic diversity in an ecosystem is important for conservation and management (Laikre et al., 2010). The genetic approaches to conservation are rarely used, especially in multi-species projects, because of the vast sampling effort and costs involved in the techniques (Wennerstr”m et al., 2013); on the other hand, the knowledge about the importance of gene flow in meto-populations informs common management practices such as providing or maintaining connectivity between populations where possible by means of maintaining hedgerows or installing wildlife corridors for example (Kaligaric” et al., n.d.).