What is biodiversity?
	How much biodiversity is there?
	Why is biodiversity so important?
	Is biodiversity threatened and why?
	What is the situation in Saudi Arabia ?

What is biodiversity?

Biodiversity (or biological diversity) is used to refer to the variability among living organisms. By the definition used by the Convention, ‘biological diversity’ means:

The variability among living organisms from all sources, including, inter alia terrestrial, marine and other aquatic ecosystems and the ecological complexes of which they are a part; this includes diversity within species, between species and ecosystems.

The most obvious differences are often those to be found between different species. A species is a group of organisms that are sufficiently similar to one another to be able to interbreed in nature and produce fertile offspring. Each species has its own particular specialisations to fit it to its own niche or place in the environment. Through external changes (such as alterations in climate or decimation of populations through predation or disease) or internal ones (such as changes in genetic composition), many species have become extinct. There are therefore far fewer species alive today that there were in the past, and this loss of species (and therefore of biodiversity) has accelerated in the past few hundred years through the increasing impacts man has on the environment.

As indicated in the definition above, variation is also found within species: each individual plant or animal has its own unique set of genes and therefore its own unique characteristics. This uniqueness allows each individual to interact with its environment in slightly different ways from other individuals – it may need slightly more or slightly less of some mineral, be more or less susceptible to disease or poisons and so on.

When the numbers of individuals (i.e. the abundance) of a species decreases, the total genetic variation within a species is also usually reduced. The species is then less well able to cope with changes in the environment and hence is more likely to become extinct when a change occurs.
In addition to the two levels just mentioned, life on earth shows great diversity within and between different ecosystems. Different external conditions, habitats within each ecosystem and different kinds of interactions between species in ecosystems mean that the functioning, nature of resources provided, resilience to change and the sustainability of exploitation of ecosystems all vary widely even within broadly similar climatic regions. This provides the third level of biological diversity.

Biological diversity is often Measurement at three levels:

SPECIES

Species diversity requires far more detailed study that can be provided by ecosystem inventories and identification of indicator species. Three measures are needed to record species-level diversity, namely, species richness, species structure and species uniqueness.

Species richness is the simplest measure, and is just the numbers of species in an area. The methods used to compute and report species richness differ and usually only easily-recorded organisms such as higher plants, larger reptiles, mammals and birds are included in inventories. This means that it is often difficult to compare between different inventories (which is critically important for monitoring the effectiveness of conservation measures or to determine changes taking place over time) and entire categories of organisms – many of which play key roles in human welfare – are ignored.

Species structure refers to the distribution of different species. This requires measurement of the abundance and other measures of the distribution of a species within the environment.

Richness and structure are measures of quantity of species, not the particular kinds of species and their importance in the environment. Not all species of equally important to the functioning of ecosystems and nor are all species of equal perceived value to humankind. Species such as Acacia tortilis are central to sustained functioning of some rangeland systems. The loss of such a species would result in the collapse of the grazing system and with it many people’s livelihoods. Other species are found only in Saudi Arabia in the entire world. Such endemic plants and animals have a special conservation value attached to them and require detailed monitoring and management. Particularly where endemic or other species are under threat of extinction (i.e. the species listed in the Red Data lists), reporting of status and the actions taken by countries to conserve these species and their habitats is an important element of the national reporting process for achieving the objectives of the CBD.

GENETIC DIVERSITY

Measurement of genetic diversity is especially difficult because the genetic variation within a species can seldom be defined unambiguously in terms of a definite number of different types.

In many cases, it is best to measure genetic diversity on the basis of the structure of the diversity. For example, in some species, most of the variation between individuals is found within a single population. In such a species, conservation of one or a few large populations will suffice to maintain the genetic diversity of the whole species. Another species may show little variation within each population, but populations at different locations may be widely different. Here, the only way to conserve the genetic diversity of the species will be by safeguarding each individual population.

In light of the increasing realisation that humankind’s very existence may depend on finding and using genes for wild species for the improvement and strengthening of economically important organisms, documentation and conservation of genetic resources (i.e. genetic diversity) is a matter of critical importance. The numbers of wild relatives of domestic crops and medicinal plants that are found in Saudi Arabia attest to the responsibility that is placed on the Kingdom to protect these God-given resources.

How much biodiversity is there?

Estimates of the total number of species range from 7 to 100 million, with a probably good estimate being about 13 to 15 million species. Up to this day, only about 1.75 million living species have been identified and described scientifically. Many new species continue to be discovered each year, most of them invertebrates. During the nineties, the number of newly described species averaged 13.000 per year.

The table below shows approximate numbers of species in major groups (UNEP, Global Biodiversity Assessment, 1995):

Why is biodiversity important?

Humans depend upon biodiversity in many ways, both to satisfy basic needs like food and medicine, and to enrich our lives culturally or spiritually. Yet in an increasingly modern, technological world, people often forget how fundamental biodiversity is to daily life and are unaware of the impact of its loss

We must understand the functional role of biodiversity in order to be able to utilize ecosystems in a sustainable manner and develop 'existence' strategies, within the context of global economic, technological and climatic change.

Biodiversity measurements tell us about the interactions between ecosystem composition, structure and functioning. Biologists have argued that one of the best values for measuring biodiversity is likely to be associated with the variety of different genes that can be expressed by organisms as potentially useful phenotypic traits or different chemical, morphological, functional or behavioral characters. Because we do not know which genes or characters will be of value in the future, they are all considered of equal importance. The assumption is that the greatest value for conservation will come from ensuring the persistence of as many different genes or characteristics as possible.

Species diversity in ecosystems is directly correlated with stability, but it is not certain to what extent this relationship expresses cause and effect. Species diversity is also apparently directly correlated with community resilience. A moderately unfavorable limiting factor tends to reduce the number of less frequent species and increase the relative abundance of common species. Under conditions of heightened stress, only a few species can survive, but their relative numbers may be high. When stress becomes extreme, only a few taxa which are able to avoid the stress can survive. The remnant members of the epiflora, however, are reduced in cover (size), frequency (number), and vitality (luxuriance).

The survival of genes, species and natural communities requires the preservation of biodiversity at the genetic, species, community, and landscape levels. Each level is dependent on and inextricably linked to the other levels. For example, the continued existence of ecosystems in their present form may be dependent on the ability of 'keystone' species to compensate for changes in the environment, which in turn is a function of their genetic variability and their ability to mutate. Humans are also linked at all levels of this hierarchy

Is biodiversity threatened, and why?

There are many ways in which the introduction of non-native or exotic species negatively affects our environment and the diversity of life on our planet. The statistics are startling and more attention must be paid to the problem and devising a solution before the cost is more than we can bear.

Compared to other threats to biodiversity, invasive introduced species rank second only to habitat destruction, such as forest clearing.

Growth in the human population has been rapid in the past decades, resulting in many and varied socio-economic challenges to maintenance of biodiversity. Traditional demands – such a need for food, pasturage for animals and the like - for all kinds of resources has obviously increased. This has both put more pressure on harvesting of natural resources, increased the use of commercial crops and animal breeds, increased use of underground water and changed farming practices. Simultaneously, livestock owners have become more independent of rainfall through easy access to financial support for supplementary feed and water tankers. In addition, the need for outdoor recreation has increased as more and more people spend their lives in cities. These changes have resulted in increasingly unsustainable use of natural resources and consequently, decrease in biodiversity.

What is the situation in Saudi Arabia ?

The term biological diversity often conjures images of particular landscapes with their plants and animals – the richness of coral reefs or the majesty of Arabian oryx in the dunes of the Rub al Khali. This aesthetic value is very important for the health and well-being of people and the increasing willingness of people to pay (sometimes to pay very high prices) for nature-based tourism, these natural habitats are by no means the only aesthetic values of diversity. Diversity in the local environment – especially for city dwellers – may be even more important. When nature is impoverished or suppressed, we suffer deprivation of physical, mental and spiritual well-being. Maintenance of biodiversity is an essential part of meeting deeper-seated needs of humankind and a nation that neglects this aspect of planning and management will ultimately suffer for its lack.

There are also practical, tangible benefits of biodiversity: it provides a wide range of useful biological resources. Fishing, and gathering of foods and medicines from natural communities are still important to the economy of the country. Sustainable use of such resources depends on conservation of the species used, their habitats and the maintenance of the functioning ecosystems of which they are an integral part.

Apart from individual species that we use, the very existence of life on the planet depends on biological processes. In all likelihood, loss of an appreciable proportion of biological diversity will result in the demise of humankind. The balances of oxygen and carbon dioxide in the atmosphere are maintained by plant life, whereas in diverse and rich communities, microbes maintain soil formation and the balances of fertility of soils. It is likely that fewer organisms than are now present could sustain all the processes that go to make the earth a functioning system. However, we do not have any idea of just what is the limit to impoverishment of fauna an flora before function ceases. What we do know is that if the global ecosystems became dependent on only a few key species (in other words, they came to resemble crop mono-cultures), an epidemic of some kind could render the entire system non-functional. Biological diversity is therefore essential to the survival of humankind and its preservation is the responsibility of every society on earth. This is especially relevant in Saudi Arabia, where many of the ecosystems have small numbers of species and hence little in-built redundancy.