Attish Kanhai
What does an oasis have in common with a coral reef?
No, this is not the start of a bad joke or a riddle (although the obvious answer is probably water), but have you ever wondered how oases occur in the desert? How can these areas flush with trees and shrubs, teeming with life, occur in the barren, arid desert environments? If you haven’t, then take a moment to ponder. It is probably not what you think. While there are many different factors that give rise to the creation of desert oases, one of them might be very surprising. It begins with organisms not visible to the naked eye.
Microbes in Israel’s Negev desert are uniquely suited to their environment. The bacteria and cyanobacteria have developed a method of binding the sand into a black crust by secreting long-chain sugars. This allows their colonies to maintain moisture during intense desert heat. These black crusts also benefit other organisms making their homes in the desert environment.
These crusts increase water retention by about 30 per cent after a downpour. Holes dug by desert porcupines (I didn’t know these existed either) allow some of this water to be retained which leads to the formation of miniature oases with many different plant species. These pools allow wind-blown seeds to find a home and germinate which, in turn attracts many other species seeking refuge from the harsh arid desert environment. These microbes that produce an entire ecosystem by their presence can be termed ecosystem engineers.
Engineers are not just people wearing hard hats and high-visibility vests holding a clipboard in some sort of construction site doing very important calculations in order to make their project successful. Engineers are responsible in large part for many of the innovations that make everyday life more comfortable. Life would be unrecognisable without the contributions of engineers.
Nature has its own share of engineers responsible for making the life of their fellow ecosystem inhabitants a little bit more bearable. They may not don hard hats and high-visibility vests, and I dare to suggest they do their calculations in their head, but without these hardworking and industrious fellows, the landscape of nature might look very different.
The term ecosystem engineer refers to organisms that cause some sort of change, either directly or indirectly, to an environment that would not occur without their presence. In so doing they modify, maintain and/or create habitats. This allows other organisms to benefit from these habitats.
Ecosystem engineers are classed into two broad categories: autogenic engineers, which are organisms that modify the environment using their own bodies such as their living or dead tissues, coral reefs for example; allogenic engineers have the ability to use non-living materials to change the physical state of the environment. The best example of this is human beings. Humans have admittedly taken the concept of allogenic engineering to a whole other level.
The sphere of influence of ecosystem engineers re
