The megabiota are disproportionately important for biosphere functioning

Brian J Enquist,Yadvinder Malhi,Michael B J Harfoot,Christopher E Doughty,Andrew J Abraham

doi:10.1038/s41467-020-14369-y

Abstract

A prominent signal of the Anthropocene is the extinction and population reduction of the megabiota—the largest animals and plants on the planet. However, we lack a predictive framework for the sensitivity of megabiota during times of rapid global change and how they impact the functioning of ecosystems and the biosphere. Here, we extend metabolic scaling theory and use global simulation models to demonstrate that (i) megabiota are more prone to extinction due to human land use, hunting, and climate change; (ii) loss of megabiota has a negative impact on ecosystem metabolism and functioning; and (iii) their reduction has and will continue to significantly decrease biosphere functioning. Global simulations show that continued loss of large animals alone could lead to a 44%, 18% and 92% reduction in terrestrial heterotrophic biomass, metabolism, and fertility respectively. Our findings suggest that policies that emphasize the promotion of large trees and animals will have disproportionate impact on biodiversity, ecosystem processes, and climate mitigation.

Highlights

A prominent signal of the Anthropocene is the extinction and population reduction of the megabiota—the largest animals and plants on the planet
One of the primary signatures of the Anthropocene has been a progressive elimination of the largest organisms[5,6,7,8], especially if one of the first antecedents of the Anthropocene is argued to be the decimation of the Pleistocene megafauna[9]
Human activities are disproportionately impacting the largest animals and trees[2,8]. This downsizing of the biosphere started in the Late Pleistocene with the extinction of much of the megafauna and continued through the rise of human societies marked by the exploitation of forests, ongoing hunting of large animals and clearing of land for agriculture and industry[10]

Summary

Introduction

A prominent signal of the Anthropocene is the extinction and population reduction of the megabiota—the largest animals and plants on the planet. We extend metabolic scaling theory and use global simulation models to demonstrate that (i) megabiota are more prone to extinction due to human land use, hunting, and climate change; (ii) loss of megabiota has a negative impact on ecosystem metabolism and functioning; and (iii) their reduction has and will continue to significantly decrease biosphere functioning. Human activities are disproportionately impacting the largest animals and trees[2,8]. This downsizing of the biosphere started in the Late Pleistocene with the extinction of much of the megafauna and continued through the rise of human societies marked by the exploitation of forests, ongoing hunting of large animals and clearing of land for agriculture and industry[10]. Human conflict frequency (warfare etc.) predicts variation in population declines among wild large herbivores in protected areas in Africa, the last significant megafaunal continent, from 1946 to 201021

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