There are in fact four levels of biodiversity: genetic diversity, species richness, ecosystem diversity and landscape diversity and biodiversity also depends upon and encompasses processes, as well as entities. These processes include, but are not limited to, biogeochemical cycles; biotic and abiotic disturbances; predatorprey, mutualistic, or parasitic relationships; migrations; competitive effects, and so forth. Thus, biodiversity includes all the entities of the living world at various levels of biological organisation, plus the various things that those entities do [5].
The ecosystem approach is described as a strategy for management of land, water and living resources that promotes conservation and sustainable use in an equitable way). It is based on the application of appropriate scientific methodologies focused on levels of biological organization which encompass the essential processes, functions and interactions among organisms and their environment, and among ecosystems. It recognizes that humans, with their cultural diversity, are an integral component of ecosystems.
The ecosystem approach should consider all forms of relevant information, including scientific and indigenous and local knowledge, innovations and practices.
The assessment of biodiversity should include identification and monitoring of ecosystems and habitats as well as identification, monitoring and assessment of species.
In order to accelerate environmental research without having to wait for results from traditional taxonomy, which is perceived to be slow to deliver because it is based on monographic treatments, new methodologies have been developed for assessing biodiversity. These include inventories, surveys, rapid biodiversity assessment, monitoring, and the use of indicator species. Rapid-assessment methods and sampling for indicator species are designed to monitor selected biotopes of critical value . Base-line studies of pristine or near pristine biotopes are required against which "trouble spots" are monitored. Medium-levels identification skills are necessary. Collaboration between staff with parataxonomic skills is necessary.[7]. Further, monitoring changes in biological diversity at the species level essentially entails monitoring changes in the distribution and abundance of species. For many species this is likely to need detailed monitoring and population modeling over decades [8].
However several studies have shown that higher taxon richness (using genera or families) is a useful surrogate for species richness, and ultimately a more remote surrogate than species for gene or character richness [9][10][11][12].
Another common solution to the impossibility of performing complete counts of organisms is to select certain taxa as "indicator group" to act as surrogates for the whole biological diversity. The use of indicator species, that is species whose status provides information on the overall condition of the ecosystem and of other species in the ecosystem, is encouraged by the SBSTTA [8].
Planned use of Geographic Information Systems (GIS) , one of the most productive avenues for the development of biodiversity assessment. may obviate the need to develop the complex habitat and ecosystem classifications.
This is because representations of different, measurable attributes of the environment can be stored in separate layers within a GIS. Examples of such attributes are: soil characteristics; altitude; rainfall; percent canopy cover; mean height of dominant vegetation; and distributions of individual species. The baseline maps used may be generated from satellite data, aerial survey, and existing maps, or created by field survey and expert advice. Different combinations of these disaggregated data sets can be chosen to generate maps according to need, without having to choose a predetermined classification system.. Such systems also lend themselves to extrapolation in that, for example, species distributions can be predicted in unsurveyed areas on the basis of congruence in environmental characteristics with areas known to contain the species [8]
Ecosystem structure variables are most promising indicators of biodiversity because they can offer a lot of information on the state of ecosystems over large areas for relatively low effort. Many aspects of quality can be captured by identifying key-ecosystem structure variables which can indicate if the ecosystem is functioning correctly or not. For example, a crude measure of quality might be the total number of well-specified habitat types observed within a sample area(s) relative to the postulated baseline number. Depending on the area and the available capacity they might be both short term and long measures. Remote sensing techniques will play a major role in this category [13]. .
These generally use indicator groups (for example the GAP Analysis Program (US Geological Survey) employs vertebrates, while Rapid Ecological Assessment (The Nature Conservancy) utilises birds, mammals, butterflies and vascular plants).
Of particular interest is the utilisation of gradient-directed sampling by National Conservation Review (Shri Lanka Forest Department) Transects are selected deliberately to transverse the steepest environmental gradients present in the area, while taking into account access routes. This technique is considered appropriate for rapidly assessing species diversity in natural forests, while minimising costs, since gradient transects capture more biological information than randomly placed transects of similar length. Also interesting is the creation by Rapid Biodiversity Assessment (MacQuarie University) of locally functional schemes for classification and identification to be used as an alternative to formal and correct species identification by expert taxonomist [8]