Almost every living thing is reliant on another for its continued existence, and our species is no different. The relationships between organisms are often bewilderingly complex, and this is part of what makes life so beautiful.
There are two main arguments as to why this is worth preserving. As the only intelligent species we have a moral obligation to do our best to preserve life in all its forms wherever we may find it; for those forms exist nowhere else in all the universe and once they are gone, they are gone forever.
For those who aren’t naturally passionate about their environment, consider the second argument.
Humanity is utterly reliant upon its natural environment for what are sometimes called “natural services.” The very air, water and soil that we take for granted have been rendered available to us by living organisms, and the waste we return to these systems is assimilated by other living things, allowing us to continue enjoying clean air, pure water and fertile soil.
The organisms we rely upon in our daily existence are themselves reliant upon still other organisms, who in turn are reliant upon still more and so the web expands. We can never know the full extent of any knock-on effects when any organism is removed, and we’ve been busy removing organisms from just about every environment since before the industrial revolution. Luckily for us there is a lot of redundancy inherent in these systems, meaning if one strand of the web fails, another can usually take up the slack. This is an example of a dynamic equilibrium.
It is biodiversity which forms this redundancy. The problem for humanity is that for every species which vanishes from any given environment, the level of redundancy is reduced. If this goes on long enough, the system becomes less and less robust until the slightest disturbance can lead to the collapse of the entire web like falling dominoes. The kicker is that natural services are no longer delivered to that environment, meaning the people there will suffer, and suffer badly. When these people move, they take the source of their problems with them.
And this is why biodiversity matters. Because we like to have enough food to eat, water to drink, and air to breathe we should care about this.
Extract from http://sciencedissected.wordpress.com/2012/06/01/why-biodiversity-matters/