Abstract
Herbivores have important impacts on ecological and ecosystem dynamics. Population density and species composition are both important determinants of these impacts. Large herbivore communities are shifting in many parts of the world driven by changes in livestock management and exploitation of wild populations. In this study, we analyse changes in large herbivore community structure over 66 years in Norway, with a focus on the contribution of wildlife and livestock. We calculate metabolic biomass of all large-herbivore species across the whole region between 1949 and 2015. Temporal and spatial patterns in herbivore community change are investigated and we test hypotheses that changes in wildlife biomass are driven by competition with livestock. We find that total herbivore biomass decreased from 1949 to a minimum in 1969 due to decreases in livestock biomass. Increasing wild herbivore populations lead to an increase in total herbivore biomass by 2009. Herbivore communities have thus reverted from a livestock dominated state in 1949 (2% of large herbivore metabolic biomass comprised of wildlife species) to a state with roughly equal wildlife and livestock (48% of metabolic biomass comprised of wildlife species). Declines in livestock biomass were a modest predictor of wildlife increases, suggesting that competition with livestock has not been a major limiting factor of wild herbivore populations over the past decades. Instead there was strong geographic variation in herbivore community change, with milder lowland regions becoming more dominated by wild species, but colder mountain and northern regions remaining dominated by livestock. Our findings indicate that there has been notable rewilding of herbivore communities and herbivore-ecosystem interactions in Norway, particularly in milder lowland regions. However, Norwegian herbivores remain mostly regulated by management, and our findings call for integrated management of wild and domestic herbivores.
Highlights
Large herbivores drive ecological and ecosystem dynamics in many terrestrial ecosystems [1,2,3]
Total large herbivore metabolic biomass across Norway decreased from 127 kg km-2 in 1949 to a minimum of 72 kg km-2 in 1969
An increase in wild herbivore metabolic biomass was behind the rise in total herbivore biomass from 1969 to 2009, and this was largely due to increases in moose and red deer biomass (Fig 1)
Summary
Large herbivores drive ecological and ecosystem dynamics in many terrestrial ecosystems [1,2,3]. Humans have facilitated great increases in the abundance of livestock, which have functionally replaced wild herbivores in many parts of the world [11,12,13]. Such shifts in herbivore communities are concurrent with other environmental changes such as changing climate patterns [14], woody plant expansions [15] and altered forestry management practices [16]. Such changes can have differential impacts on livestock and wild herbivore fitness [17]. In light of rapidly changing environments around the world, we need a deeper understanding of how environmental factors, which occur alongside socio-economical factors, drive shifts in herbivore assemblages
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