I’m continuing to plough on with Darwin’s Origin of Species, though as with so many resolutions, the aim of reading 16 pages a day has rather gone by the wayside. So far I have covered Variation under Domestication, Variation under Nature and The Struggle for Existence and I remember now why I gave up the last time I tried to read it, it’s not so much like wading through treacle as trying to catch fireflies in a swamp.
As I mentioned last week, context is everything, I have to remember that Darwin is very much feeling his way in the dark, but as he does so, he is stumbling on the principles of heredity, genetics, ecology and resource management. He is beginning to see that each species and their population are affected by the space/food available to live, the features they have inherited from parents that might give them a competitive advantage and the relationship that plants and animals have with both the other organisms that live around them and the climate in which they exist.
Over time, our knowledge of genetics, ecology and many other related subjects has grown exponentially, whereas at the time of writing, this was all emerging science. So Darwin flits from one area to another much like the ‘Humblebee’ he describes in The Struggle for Existence. By this point he has made a link between the populations of bees and clover. He hypothesizes that if the bee population died out, so would the clover, as the plant is pollinated solely by bees.
Bringing this debate right up to date, we now know that modern fruit production without bees would be totally unsustainable, and we rely on them to pollinate a huge range of our food. Yet bee populations are under pressure and are in huge decline, there is a lot of debate around why this is the case, parasites and disease have played their part, but so has human influence with use of insecticides and loss of habitat.
Staying with the importance of population for a moment, Darwin would have been aware of the geographer Thomas Mathus, who published his Essay “The Principals of Population” in 1798. Malthus had noticed that an increase in food production led to an increase in population size; but that the increase was temporary, as famine, disease or a catastrophe such as war, would bring the population back to sustainable levels. These are known as the Malthusian Principals, and any self respecting student worth their salt can work them into any given Human Geography essay – ahem… or maybe that was just me.
Moving on… Darwin goes on to talk about predator prey relationships, i.e. how one population is affected by an other, for example how field mice affect the population of bees (and the production of honey) as they eat the combs; meanwhile the mouse population can be affected by the presence of a cat. This is a simple food chain, once you start bringing other species into the frame the situation becomes more complicated and you can build up a food web. Science will later go on to discover just how inter related species are. In fact we are still discovering this which is why the deforestation of rainforests, and the bleaching of coral reefs are such catastrophic events as these habitats have the richest biodiversity on the planet and risk being lost forever.
A recent development in this area was the reintroduction of wolves to Yellowstone National Park where a cascade effect has become evident. This is the subject of much study and the wider effects of the reintroduction are still coming to light but in summary; the elk population was out of control following the elimination of wolves in the 1920s and the decision was made to reintroduce wolves, this happened in 1995. Since then all sorts of changes have been observed.
The population of Elk remains stable, but their behaviour has changed, they move around more, which has helped willow and other shrub species regenerate, this in turn has supported the beaver population which has increased. The increase in beaver activity (stop the giggling at the back!) has affected the course of the river and the speed of water flow, supporting an increase in insect and fish populations. Also there are more elk carcases available through the winter which has supported populations of ravens, coyote, fox and a range of other animals. The whole ecosystem is affected by the presence or absence of the top predator.
As I mentioned above, the fields of science that Darwin alludes are now specialist areas in their own right and in the space of a sentence he moves from talking about food webs to the adaptation of species according to their habitat and then on to inherited features and what will become genetics. It is difficult to follow, as before one thing is explained fully, we move on to another ‘big idea’.
Approaching the end of the chapter, the luxury of hindsight makes me take issue with some things. Darwin talks about the idea of taking a native species out of it’s natural habitat and relocating somewhere else, where environmental conditions are similar, this is of interest to him and he will later experiment with plants using wind pollination and seed dispersal. Later scientists, explorers and eventually ordinary people will be responsible for huge population dispersals which is how we come to have pests like the Cane Toad in Australia, Japanese Knotweed in Europe, Grey Squirrels in Britain and a range of other invasive species that threaten indigenous populations.
He ends with a thought that gives him some comfort, in that at least the war of nature isn’t incessant, no fear is felt and that death is always prompt, that would be lovely, but again, with improved scientific knowledge, unfortunately I beg to differ.