Ecological communities - a thorny issue?

News | Posted on Monday 29 January 2024

Postdoctoral Research Associate Jack Hatfield discusses Ecology and biodiversity change, including the turnover of species and the losses and gains that change generates.

“It is interesting to contemplate a tangled bank, clothed with many plants of many kinds, with birds singing on the bushes, with various insect flitting about, and with worms crawling through damp earth, and to reflect that these elaborately constructed forms, so different from each other, and dependant upon each other in so complex a manner have all been produced by laws acting around us.” Charles Darwin, The Origin of Species.

Ecology is often seen as the study of the relationships between different organisms. It is therefore interested (especially community ecology) on how this tangled bank is organised and functions. Theoretically an ecological community is composed of the complete set of organisms living in the same place at the same time. These all interact and influence each other to at least some extent in a number of complex ways.

The vast majority of studies however focus on a specific subset of this, for example mammals or plants. There are many practical (eg consistent survey methodology) and ecological (eg most intense competitors, most similar requirements) for this but how does such an approach influence our views on biodiversity change?

Firstly, it is widely reported that we know more about certain groups (e.g. birds) than others (eg insects). This has a huge impact on our knowledge of biodiversity. There is also the issue of if we are really comparing the same thing. A study on plants for example covers a whole kingdom in the tree of life whereas mammals are just one small class in the kingdom Animalia (animals). In the marine world similar parallels could be drawn between surveys of benthos (organisms living on or near the bottom of the sea) which contains various branches of the tree of life compared to another that focuses just on vertebrate fish.

Biodiversity change is all about losses and gains, the turnover of species. Do we always expect this turnover to happen within a particular relatively narrow grouping? Perhaps not. Darwin’s tangled banks illustrates how all species in a community are interlinked and years of research on population biology, food webs, trophic cascades and more have shown that changes to one section of a community will influence another. At least some ocean ecosystems may be changing from being dominate by fish to being dominated by jellyfish with overfishing and climate change in the dock. Studies of logging have seen roles shifting between invertebrates and vertebrates. As useful and insightful as these studies are many of these multi-trophic, multi-taxa studies remain localised (presumably because they are finance and time hungry).

Given these challenges is current practice sufficient? How does it affect our conclusions, and do we need to change it? Can more of macroecology expand the communities of study?

Find out more about Jack Hatfield's research