Environment, Ecology & Earth's biodiversity

[Sully]

Interesting paper which has been used to argue that there isn't actually an unnaturally high population of deer in the UK, due to the biomass-productivity relationship. Flawed however as there is a marked ecological difference in the spatial organisation between grazers and browsers. Still, worth thinking about, and true that any amount of deer without predation will supress woody growth. and it wasn't a deer overpopulation which originally felled all the trees. 

Exploring a natural baseline for large-herbivore biomass in ecological restoration

Abstract

1. Large herbivores provide key ecosystem processes, but have experienced massive historical losses and are under intense pressure, leaving current ecosystems with dramatically simplified faunas relative to the long-term evolutionary norm. Hampered by a shifting baseline, natural levels of large-herbivore biomass are poorly understood and seldom targeted. This ‘Decade of ecosystem restoration’ calls for evidence-based targets for restoring the natural diversity and biomass of large herbivores.
2. We apply the scaling of the consumer–producer relationship to a global dataset of large-herbivore density in natural areas. The analyses reveal that African ecosystems generally have much higher large-herbivore biomass and also the strongest consumer–producer relationship. For Europe, Asia and South America, there are no significant relationships with primary productivity indicative of impoverished faunas. Compared to expectations from the African scaling relation, large-herbivore biomass in ecosystems outside Africa is considerably lower than expected.
3. Synthesis and applications. Ecological restoration and rewilding entail restoration of a natural grazing process. Our findings indicate that many nature reserves are depleted in large-herbivore biomass, judged from their primary productivity. Meanwhile, overexploitation by seasonal livestock grazing takes place in other areas. It is thus difficult, but urgent, to reach scientific consensus regarding a natural baseline for large-herbivore biomass. Until such agreement has been reached, we recommend to manage, or rewild, large herbivores in year-round near-natural grazing and without predefined density targets, but following natural and fluctuating resource availability with minimal management intervention. The establishment of experimental rewilding sites with reactive herbivore management is needed to further advance our understanding of natural grazing density.
   

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