Exploring a natural baseline for large herbivore biomass

Abstract

The massive global losses of large mammals in the Pleistocene have triggered severe ecosystem changes including changed nutrient cycles, fire regimes and climate, shifts in biomes and loss of biodiversity. Large herbivores create and diversify resources and living space for other organisms and thereby play an important role in ecosystem functioning and biodiversity conservation. However, even today large herbivores are regulated, hunted and driven to extinction to a degree where intact large-herbivore communities are largely non-existent. Consequently, natural density and biomass of large-herbivores for restoration of ecosystems are poorly known. To address this knowledge gap, we apply the scaling pattern for consumer-producer relationships and show that the biomass of large herbivores in ecosystems across the world is considerably lower than expected from primary productivity. African ecosystems have the strongest consumer-producer relationship and assuming that African ecosystems approach a natural baseline, we use this relationship to predict large herbivore biomass in Europe as an example. Our findings indicate that restoring large herbivore biomass would entail increasing large herbivore biomass by orders of magnitude in most ecosystems, which potentially changes the perspective on large herbivores in conservation and restoration projects.

Extinctions have strongly reduced the mammalian consumption of primary productivity

“…Mapping total mammal biomass, we get comparable estimates to what others have found before, based on empirical local animal counts 24 . Fløjgaard et al 24 report a bimodal distribution of empirical large-herbivore biomass in Europe with the high numbers, from rewilding sites, in line with our estimates. Comparing to the empirical values from their study based on animal counts we find that our theoretical estimates are broadly in agreement, but for most areas in the Afrotropics tend to be higher than those observed empirically (Fig S6).…”

“…Mapping total mammal biomass, we get comparable estimates to what others have found before, based on empirical local animal counts 24 . Fløjgaard et al 24 report a bimodal distribution of empirical large-herbivore biomass in Europe with the high numbers, from rewilding sites, in line with our estimates.…”

“…Total current biomass in protected areas. Data of herbivore biomass estimates based on population counts from Fløjgaard et al 24 mapped against this study’s median results in the same areas (for their current fauna). (a) Is all global data and (b) is a zoomed region showing more detailed info outside the Afrotropics.…”

Rapid Anthropocene realignment of allometric scaling rules

“…Other authors have argued that natural baseline could be estimated by focusing on historically less impacted regions of the world (e.g. Africa; Floejgaard et al . 2020).…”

Rapid Anthropocene realignment of allometric scaling rules

“…Other authors have argued that natural baseline could be estimated by focusing on historically less impacted regions of the world (e.g. Africa; Floejgaard et al 2020), yet several studies have shown these regions to be have also been substantially negatively impacted by humans (Malhi et al, 2016; Newbold et al, 2016). A different and promising avenue of research, would be estimating ‘natural’ abundances through the use of mechanistic ecosystem models, for example, the Madingley model (Harfoot et al, 2014).…”