One fascinating attribute of an ecosystem is the diversity of species that make up the system. A diversity of functional groups is naturally to be expected because the food webs in an ecosystem involve autotroph, herbivores, carnivores, detritivores, and so on. But surprisingly, a diversify of species exists within each functional component. For instance, if you collect, some phytoplankton using plankton net from a nearby pond, chances are that you will find more than 20 species of algae.
Diversity of living organisms appears to be a feature of our entire biosphere, something that attracted the attention of naturalists for centuries. When one realizes that there are more than 3 lakh different species of beetles on this planet, nearly 200,000 species of fishes and probably many more waiting to be discovered, one naturally becomes curious about the evolutionary and ecological factors that had been responsible for such great diversification.
As a parameter, species diversity by itself is not so informative because the term is relative. If you told that a particular community has 14 species of birds, you would not know if that value represents a low diversity or high diversity unless you compare it with bird species diversity in another community.
However, it is the geographical patterns in species diversity seen in our biosphere that tell us a lot about the factors contributing to diversity. One of the most noticeable patters is that species diversity on earth is maximum in the tropics and decreases progressively towards the polar areas. Take birds for example – Colombia, situated near the equator in the tropics has nearly 1400 species of birds, while New York State in the temperate latitudes has 105 species, and Greenland, situated close to the north pole (70o latitude) has only 56 species of birds. Our country, much of which lies in the tropics, also has a high diversity of bird species, more than 1000.
Plants also show similar trends – there are nearly 2,000 species of vascular plants in the temperate state of Ohio (USA), but 20,000 of them in small country Ecuador, situated on the equator. Species diversity is more on continents than on islands at the same latitudes. Besides, the latitudinal trends it is seen that species diversity is less in high altitude ecosystems.
The rich variety of flora and fauna we have around us is part of our natural heritage, and we have to ensure that human activities do not despoliate this great diversity and leave a poorer biosphere for the next generation. One way is to monitor the species diversity of ecosystems that are subjected to the ravages of human influence such as pollution and deforestation. Like energy transfer and productivity, species diversity of a community is also a measure of its health and well-being.