Most scientific definitions of ecosystem function focus on individual functions such as carbon sequestration, water filtration, primary production, etc. I think of these more as ecological functions, individual functions that we can describe within a functioning ecosystem. But how do we define the functioning of an ecosystem as a whole? Ecosystem function is the extent to which living processes transform solar energy into complex trophic structures, assimilation pathways with highly evolved information (DNA) content, and internal biotic regulation. Ecosystems function at scales from my stomach, to the living Earth system, or Gaia. Net primary production (NPP), or the total amount of biomass growing in one place in one year, is often used as a proxy for ecosystem function. Unfortunately, measurements of NPP do not consider how that production is being transformed and assimilated into the ecosystem through trophic webs. In fact, it is difficult to measure NPP in areas with high functioning, because the biomass is being regularly consumed by herbivorous insects and animals. A more effective proxy for measuring ecosystem function is land surface temperature. Higher functioning ecosystems are more effective at degrading solar energy, and thus do more work. Ecosystem work involves the transformation of solar energy using the latent heat of vaporization of water. Thus, tropical forests are cooler than deciduous forests because more work is being done transforming water and sunshine into plant, animal, insect, bacteria, and fungal biomass and information. Thus for areas with equivalent incoming solar energy, higher functioning ecosystems have cooler surface temperatures.
Kay, J. 2000. Ecosystems as Self Organizing Holarchic Open Systems: Narratives and the Second Law. Handbook of Ecosystem Theories and Management. CRC Press – Lewis Publishers.
Odum H.T. Environment, Power, and Society for the Twenty-first Century. Columbia University Press: 2007.
Schneider, E.D., and J.J. Kay. 1994a. Complexity and Thermodynamics: Towards a New Ecology. Futures 24(6)
Schneider, E.D., and J.J. Kay. 1994b. Life as a Manifestation of the Second Law of thermodynamics. Mathematical and Computer Modeling 19(6-8).