The natural world has been around for a very long time. Every living organism is testament to individual survival and the biological sustainability of its species over many aeons. Looking around at the natural wonders surrounding us, it is evident that nature can show us as individuals and species how sustainability should work.

Life is sustained by energy. The intricacies of the food web within an ecosystem show how energy is transferred throughout the entire system, each part being reliant on the others for survival, just as humans have built up their own system of energy flow from farm to table.

Natural organisms ensure that their energy flow is not affected by outstripping or damaging the resources they rely on, and to do this, they limit their use of resources or adapt to new ones. This can be seen in highly specialised animals such as cheetahs, which rely on medium-sized antelope as prey. Generalists, such as the leopard, will change their diet when needs be. Interestingly, specialised animals are fewer in number and more prone to disruptions in the energy flow than generalists, which is why there are still leopards in the Cape mountains, but no cheetahs.

This can also be seen with the migrations that occur once energy levels drop, whether through seasons or drought. The annual migration of swallows and other birds is well known. The modern migration of humans from poorer, drought-stricken countries towards more resource-rich areas is also proof of this. We will see more of this happening as the effects of climate change become more severe.

It is only when there is enough energy in the ecosystem that reproduction can take place. On a species basis, for a species to survive, two individuals only need to produce two offspring that make it to adulthood during their lifespan. Any other offspring that survive add to the numbers, and the species flourishes. There are two distinct breeding strategies, one where a myriad of offspring are produced with very little input from the parents, insects being an excellent example of this, and another where few offspring are produced, but the parents ensure survival by putting a lot of energy into their offspring – as in elephants and humans; both strategies work, but larger, more complex organisms predominantly use the second.

Raising offspring to breeding age and thus ensuring genes pass over into a new generation is one of the strongest urges in the natural world. In real terms, only the strongest members of a species get to breed, and of the surviving offspring, only the top five percent will ever breed successfully. The adage of ‘survival of the fittest’ rings true.