This Saturday, the 22nd of May, was the International Day for Biological Diversity. But, what exactly does this term mean?
Biodiversity is the variety of life on our planet – but it is not only a number of different species. While species richness gives us the number of different species in a certain area, biodiversity is much more than that.
Biodiversity includes:
- diversity within a single species – genetic diversity, gene variability
- diversity among species – number of different species in a certain area (species richness)
- ecosystem diversity – total number of different ecosystems at a certain area
As you can see, biological diversity is a complex term that includes several levels, beginning with a study of genetic material in only one species, and ending with vast ecosystems that include hundreds or thousands of species.
Several weeks ago I visited one of Croatia’s national parks with beautifully preserved forests – Risnjak National Park. The first thing that I noticed, only several hundred metres past the entrance, were voles. Vole is a rodent similar to a mouse, and it was the first time I have encountered it out there in the wild, during a day and only 2-3 metres from me.
“My time in the Park has hardly begun, and I’ve already seen a vole! What’s next?”
But the truth is, voles were the only mammals (except humans and dogs) that I saw that day. A lot of voles – jumping across fallen leaves quite noisily, hiding in their holes, watching me carefully, accidentally falling off tree logs – they were everywhere.
At first glance, someone might say that species richness in that area is poor – one species of mammals in great abundance. But Risnjak is an area of great biodiversity, and one walk during the day is far from enough to estimate species richness of that locality.
Biodiversity assessment requires a lot of scientific knowledge. Some surveys last for years, and some even for decades.
When evaluating a certain area’s biodiversity, scientists explore two parametres: species richness – the number of different species at a certain area, and relative abundance – the number of organisms of each species.
Why are those parametres important? Because they show us if an ecosystem is balanced; a balanced and diverse ecosystem is rich with species, and none of the species has a drastically high relative abundance. There are enough producers and decomposers, as well as prey and predators, to maintain a stable food web.
On the contrary, if only one species thrives, and other species are scarce in number and abundance, the food web becomes unstable and the ecosystem becomes unbalanced.
For example, if a certain top predator species becomes heavily abundant, it has a greater need for food, which leads to a reduced abundance of prey species.
Biodiversity is much more than the vivid colours of coral reefs and the loud symphony of rainforests. Maintaining biodiversity is more than keeping nature diverse and exciting.
It means healthy ecosystems, healthy rivers and forests. It means healthy seas full of fish and plankton and other species, which then support sea birds and mammals, including us.
Biodiversity is balance, and nowadays it is more and more disturbed by various human actions.
The whole natural communities depend on each other, and we depend on nature and its balance. Doing against nature, we do against ourselves.
Literature
Cleland, E. E. (2011): Biodiversity and Ecosystem Stability. Nature Education Knowledge 3(10): 14