Biodiversity indexes are the unavoidable point of departure. To infer potential species richness from samples is already a challenge, but standard packages do all the work for you. If  you do only this analysis, decision making will be based on species richness. So other criteria should be incorporated in decision making for habitat conservation. Something on diversity of ecological functions and on services provided, at least, should be incorporated as well in good decision making for conservation.

I agree entirely with David - a measure of ecological function is essential and simple diversity indices won't do this. If you're working with wetland habitats, Community Conservation Index (CCI) could do the job for you. It incorporates a rarity weighting as well as a measure of richness. You can download the paper from my profile page.

Krizler,

In addition to the points mentioned by the colleagues, You should also consider Phylogenetic diversity and analysis of complementarity.

Here are a couple of references on this subject:

http://www.sciencedirect.com/science/article/pii/0006320792912013

http://rspb.royalsocietypublishing.org/content/267/1442/505

Another useful approach, following on from Jorge's excellent reply, is to dispense altogether with species data and concentrate on habitat. You may need some taxonomic or phylogenetic data from similar habitats in order to determine whether the habitat in question is the appropriate type, but having made this decision, you can assess the value in terms of how much of an unusual habitat is there and what sort of condition it's in. We have, in large part, moved away from single species Biodiversity Action Plans and concentrated on Habitat Action Plans in delivery of the precepts of EU directives. For example, we have been mapping the extent and associated condition of  groundwater dependent wetlands and chalkstream habitats as critical environments in Europe. To be sure, an inventory of species present in these adds to the picture and analysis using indices helps in making decisions, but simply outlining the extent of geologically or habitat-structure defined areas can lead to appropriate management of these.

Thank you everyone for your insights regarding the question, from your answers it is very important first to identify criteria/standards in conserving a specific habitat because there are a lot of things to be considered. Biodiversity diversity indices may be valuable but it is necessary to integrate this with various ecological attributes. 

Thank you!

Choosing the exact index is very important. Stress index is very crucial in this context, where both opportunistic and sensitive species are given importance

Hi Krizler, I think that if you are concerned with biodiversity conservation then diversity indices are not much use: you need to look at the actual species present. The EDGE (Evolutionary Distinct and Globally Endangered) programme of the Zoological Society of London is a good example of setting priorities for species on the basis of a combination of endangerment (from the IUCN red list) and evolutionary distinctiveness. In the Philippines, you have KBAs (Key Biodiversity Areas) identified because of their global significance for conservation of particular species. There are other reasons for conservation apart from saving species (e.g. water catchments, sustainable harvest of forest products, tourism) and if these are more important then you should use indices that directly assess value for these purposes. It is difficult to think of a situation where a diversity index is best!

re:biodiversity measurement

Biodiversity must be regarded as a quality measurement with a range of properties that can be measured (normally as arange of indices).

It is the balance between these indices that defines the QUALITY of biodiversity of the target group.

As stated by Gaston and Spicer it is notpossible to measrebiodiversity by a single measurement.

This approach requires a redefinition of the term biodiversity (as definedby the CBD) since the currently used definition doesnot work!

Seemy papers in Ecological Indicators of which the paper entitled Biodiversity Quality:aparadigm forbiodiversityisthemost relevant.

Hope this helps.

Alan Feest

Following up on Corlet and Feest, note that disturbed habitats often have high species richness and diversity, but of common or 'weedy' species that are of lower conservation priority.

I would not consider species measures of less value than than 'functional' traits (the current conservation trend). In fact, the opposite. All the function in world will do little for conservation if it does not first and foremost promote species diversity.

I agree with Truman on both counts, except that some rare species (especially plants, but also some invertebrates & fish) require a degree of physical disturbance to maintain a population. We have a number of priority species where a lack of disturbance can lead to a monoculture of more vigorous species which exclude the rare ones, so we intervene. Usually with grazing, but it may need machinery.

But to get back to the point, huge diversity of common & widespread species is OK as far as it goes, but I would value a site more highly if it supported only a handful of species in it if all of them are rare and/or restricted in distribution. Classic examples here are naturally ephemeral ponds and streams, supporting such things as tadpole shrimps and insects like Metacnephia amphora, adapted for predictable ephemerality. I wholly agree that the most valuable thing in a habitat are the species it supports, but a simple notion that 'more is better' drives me bonkers!

Following Richard's comment I have now twice (Portugal and fens in the UK) observed in extensive surveys that the spiders of sites with most species have the commonest species and the sites with the fewest species have rarest species! So which should be valued highest?

Bit of a cop out, but I suppose you could say both, but for different reasons - the former is valuable in terms of its local biodiversity, the latter for its contribution to national or global biodiversity. Personally, I would still tend towards the latter, but that's just me.

Biodiversity is a very over-used word, however!

Most important is the aim of conservation. If it is habitat conserving or the biodiversity or endemit species/habitats conservation - as you know some habitat is protected for valuable ecosystem (which do not has high biodiversity) like deserts, alpine areas. So, important is the aim of conservation, but from my opinion, you have to consider all aspects - biodiversity, endemit species, rare species, rare habitats.