DEATH TO ECOLOGY!

Don’t worry. I am not fed up with my science, nor have I taken up necromancy! I am referring to the importance of death to ecology. Death is a vital ecosystem phenomenon, even if we tend to shun it. I will briefly explain why and I beg forgiveness from those of you with deeper knowledge for the simplifications of such a complex topic necessary in this short note.

Excepting a very few invertebrate animals such as certain jellyfish, planarians, some microbes and, possibly as well as perhaps surprisingly, lobsters, all living things that are not eaten or killed in various situations in which they may meet a premature doom (often at the hands of ourselves) eventually age and die. Senescence is built into their and our genes and, sad and regrettable though we may find it in ourselves or our pets, there is a very good reason for that: it supports the successful  functioning of ecosystems in an ever-changing world. A Darwinian rule for a species’ survival is that it must adapt to environmental changes around it by maintaining its “fitness” to keep on going in an uncertain and highly dynamic world. This is largely done through sex and shuffling genes so that those resulting individuals in a cohort with the “best” qualities for the environment in which they may find themselves are promoted and thus survive at least for the time being (see the graphic below on survivorship, too). This process is behind the wonderful myriad of life forms on our planet. But it also means that, as the older individuals become less well adapted to their surroundings as the environment changes, redundancy ensues and the health of the population of the species concerned as a whole would suffer if the unfit (in a Darwinian sense) and the oldies were not removed from the system. In some species, most individuals die young, on others old, and all stations in between.

Whatever the case, to my mind and most other ecologists, it follows that the evolutionary pressure for the selection of mortality must self-evidently be very high. Elimination of the individuals with genes that, in their expression, make the organism functionally less fit, is a vital service to the ecosystem and thus, in the ecological theatre where everything is connected to everything else, to us as a species in that system, even if we cannot individually, despite Google’s and others’ best efforts so far anyway, escape nature’s vicissitudes in respect of slowing aging and thwarting death.

There are many ifs and buts in this subject. One rider I should here add is that the present extinction crisis we are experiencing of fauna and flora around the world is not the “natural” ecosystem function of normal mortality we expect from a Darwinian interpretation of life: it is caused by us in our unwise, sometimes unwitting but often perfectly well understood and ruthlessly executed, if you’ll forgive the pun, attack on nature – fossil fuel abuse, land, air and water toxins, deforestation, eutrophication and what have you. (Of course, you can argue that the human species is “natural” but the semantics become horribly contorted even if fascinating – but that discussion will have to await another day.)

Betts Ecology recognise the importance of death in genetics and the maintenance of Darwinian fitness to an ever-changing environment; demise and decay are themselves associated with a richness of species that play a vital role in ecological decomposition and nutrient cycling. Perhaps, as I head at alarming speed towards my middle seventies, I think more about my certain demise than once I did, but as naturalists, maybe we all should and concern ourselves with the legacy we leave for those that come after and the health of the planet they will inherit.

 © Betts Ecology