Bio-diversity
The bio-diversity of an area is an indicator of the health of the local eco-system and also the larger eco-system which we call The Environment. It is important that our environment is healthy because it is our life support system and without it, life itself is impossible. If you think the environment is just somewhere to go for your holidays, just try this simple experiment : stop breathing the environment's air for three minutes . . .

All natural eco-systems are diverse, but some are more diverse than others. The major structural elements of eco-systems are the soil and its micro-organisms, plants, including herbs, shrubs and trees, and animals. Among the animals are herbivores which eat only plants, omnivores which eat both plants and animals, and carnivores which eat only other animals. These groupings are called Trophic Levels (literally the level at which they eat) and they are an important part of the way we analyse eco-systems.

If a field of just one kind of grass was populated only by kangaroos, then the kangaroos would either quickly eat out all the grass and then starve to death, or (if it was a very big paddock) they would gradually breed up until their numbers were roughly in balance with the available food, and then they would be on the edge of starvation all the time. In practice, the rate of grass growth isn't constant so the carrying capacity for the kangaroos will vary, and the population numbers will boom in good times and crash in bad times. Quite possibly, in such a simple eco-system, the kangaroos will be wiped out in a particularly bad season, and that's the end of your eco-system.

Now let us introduce some eagles into the paddock. Eagles feed on joeys and so when the kangaroo numbers are high, the eagles flourish and their numbers go up. This limits the kangaroo numbers and prevents the kangaroos from over-exploiting the grass, which was the reason the simpler eco-system failed. Eventually though, the eagles will start to eat so many joeys that new food becomes hard to find, and the eagles will start to starve and their numbers will fall back. This in turn eases the pressure on the kangaroos, which in turn slightly increases the pressure on the grass.

Notice how the extra trophic level helps produce a more stable eco-system. The kangaroos become both exploiters and exploited - there is both positive and negative feedback on their population numbers and this prevents wild population swings.

So far we have discussed kangaroos growing, but we haven't considered kangaroos breaking down. If our eco-system had only grass, kangaroos and eagles, before long we would be up to our ankles in manure and the grass would die out for lack of sunlight. Since about 75% of the grass that gets eaten by kangaroos ends up as manure, it obviously is made of more or less the right sort of nutrients for making more grass. To make this eco-system work properly we are going to need earthworms. They eat the manure and absorb some of the nutrients for themselves and their reproduction, and break the rest down into a simpler form that grass can absorb through their roots.

Now the more grass, the more kangaroos; and the more kangaroos, the more manure; and the more manure, the more earthworms; and the more earthworms, the more grass. Of course if you get too many earthworms, then they run out of manure and their numbers drop back, so this sub-system of the whole eco-system is self regulating too.

And don't forget the carcasses of the kangaroos that die of old age. Worms can't eat those, and eagles won't either. What we need is goannas .....

And don't forget the eagles and goannas need somewhere to build their nests. Trees would be good for that, but we need to have some insects to pollinate their flowers to produce seeds for the next generation, and we need to have some fruit bats to eat the fruits and carry the seeds off to new corners of the paddock. And some more birds to keep the insects under control.

As I hope you can see, every time you think about the eco-system, you find there is the need for another component, to help make the system more stable and sustainable in the long term. The more links in the web of life, the more positive and negative feedback loops you have, and the healthier things become. To be sure, some eco-systems like deserts seem to manage with very few species, but deserts are insecure places to live, with plagues of mice and locusts, and wild fluctuations of kangaroo numbers. The best eco-systems have many, many species and can thrive in balance for millions of years despite major climatic and geological changes.

Here at Chakoro Nature Reserve there are hundreds of species of trees and shrubs, over a hundred different kinds of birds, each species doing its own specialised thing - living in its ecological niche. As well as earthworms, we have fungi and beetles and many other insects breaking down the leaves on the forest floor and the fallen tree trunks.

We don't have kangaroos exactly, but we do have Pademelons, Agile Wallabies and Swamp Wallabies, and Northern Long-nosed Bandicoots. The bandicoots can slip through the fence around my garden, next to the rainforest, and they dig little holes in the grass, looking for worms. Then the fruit bats fly out of the forest with blue quandong fruits and hang in my lychee trees to eat them.



Some they drop, and some of them fall into the holes dug by the bandicoots. And when it rains, which it does here a lot, the soil gets washed back into the holes, covering the blue quandong, and three months later up pops a new tree. It's true ! You couldn't do it better yourself if you spent all day working at it.

Just listing all the species here is a job that would take a lifetime. I have only been at it for four years and so the list is nowhere near complete. But if you are interested in the species list so far, click below. I should like to provide notes on each species, giving information like which insects pollinate which trees, but this information has yet to be discovered. That is why it is so important to protect the bio-diversity we have now, so that we can spend the next thousand years or so compiling a complete record of the Web of Life.

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