The metabolic rate of the biosphere and its components

Significance

Assessing the relationship between energy flux and the quantity of biomass it sustains offers the potential to understand the biological “carrying capacity” for ecosystems on Earth and beyond. Our work supports this understanding by quantifying the energy–biomass relationship for the global biosphere and an environmentally diverse range of its components, and by exploring the factors—including the impact of humanity—that affect that relationship.

Abstract

We assessed the relationship between rates of biological energy utilization and the biomass sustained by that energy utilization, at both the organism and biosphere level. We compiled a dataset comprising >10,000 basal, field, and maximum metabolic rate measurements made on >2,900 individual species, and, in parallel, we quantified rates of energy utilization, on a biomass-normalized basis, by the global biosphere and by its major marine and terrestrial components. The organism-level data, which are dominated by animal species, have a geometric mean among basal metabolic rates of 0.012 W (g C) ⁻¹ and an overall range of more than six orders of magnitude. The biosphere as a whole uses energy at an average rate of 0.005 W (g C) ⁻¹ but exhibits a five order of magnitude range among its components, from 0.00002 W (g C) ⁻¹ for global marine subsurface sediments to 2.3 W (g C) ⁻¹ for global marine primary producers. While the average is set primarily by plants and microorganisms, and by the impact of humanity upon those populations, the extremes reflect systems populated almost exclusively by microbes. Mass-normalized energy utilization rates correlate strongly with rates of biomass carbon turnover. Based on our estimates of energy utilization rates in the biosphere, this correlation predicts global mean biomass carbon turnover rates of ~2.3 y ⁻¹ for terrestrial soil biota, ~8.5 y ⁻¹ for marine water column biota, and ~1.0 y ⁻¹ and ~0.01 y ⁻¹ for marine sediment biota in the 0 to 0.1 m and >0.1 m depth intervals, respectively.