I am very glad that our paper “Organising principles for vegetation dynamics” was published today in Nature Plants (https://www.nature.com/articles/s41477-020-0655-x). This perspective paper explores new approaches to modelling the terrestrial biosphere by drawing explicitly on overarching constraints on plant and ecosystem behaviour: natural selection, self-organisation and entropy maximisation.

Natural selection is the important simplifying principle underpinning the development and application of eco-evolutionary optimality theory. The concept of eco-evolutionary optimality invokes the power of natural selection to eliminate uncompetitive combinations of plant traits, and this results in predictable, general patterns in trait distribution across environmental gradients. The term eco-evolutionary optimality expresses the fact that plants adjust to environmental conditions both on short, ecological timescales and on longer, evolutionary timescales.

Eco-evolutionary optimality theory is the basis for the work of the so-called “next gen” vegetation modelling group convened by Colin Prentice at Imperial (https://www.imperial.ac.uk/people/c.prentice) and that SPECIAL has been part of for the last three years. By formulating plant behaviour in terms of trade-offs, for example between CO2 uptake and water loss, that plants are required to make, the next gen group has already made considerable progress toward building a much simpler and more robust model of biosphere processes. The P model (see Stocker et al., 2020, https://www.geosci-model-dev.net/13/1545/2020/) for example predicts gross primary production through a combination of two optimality hypotheses: (a) that stomatal behaviour can be predicted through minimising the combined costs of maintaining water loss and carbon uptake pathways, and (b) that both the enzymatic capacity and the electron-transport rate that determines the reducing power required for carbon fixation are balanced such that plants can use all the available light to fix carbon. Nevertheless, this simple model predicts gross primary production across a range of ecosystems as well (if not better) than more complex models.

The idea for the Nature Plants perspective on new approaches to modelling the terrestrial biosphere was developed at a star-studded meeting at IIASA in March 2017. So, the publication was definitely a “slow train coming” (with apologies to Bob Dylan). But perhaps ideas are like wine and get better with age.