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Biodiversity model includes indirect impact of harvesting wild species
27.05.2010 |
by: Lyubomir Penev
Researchers have developed a new model to estimate the impact of harvesting wild species and land use change on biodiversity. Unlike previous models, it considers the indirect effect of harvesting or pest control on landscape structure through reducing the variety of species.
The major drivers of biodiversity loss are the harvest of wild species and the conversion of habitat for productive purposes. Harvesting affects biodiversity by extracting desirable species and species considered to be pests. Land conversion can either reduce the number of habitats or niches, as in the case of a monoculture when only one species exists, or it can create more habitats, as in the case of the naturalisation of urban or peri-urban environments.
Environmental 'heterogeneity', or variation of habitat, within a landscape means one or few species are not able to dominate and therefore it tends to encourage biodiversity. By its very nature, harvesting affects habitat heterogeneity by taking away certain species. This produces an indirect impact on biodiversity, additional to the direct impact of the removal of species.
The research developed a model of the relationship between species richness, harvest and landscape heterogeneity to predict both positive and negative effects on the growth potential of each species. It considered the removal of species and the addition of species, both deliberately through harvesting and imported seeds or animals, and accidentally through invasive species. It also considered the increase in niches and number of species due to an environment's heterogeneity and the possible reduction of some species due to competition from a large number of species.
Firstly the model identified the privately optimal harvest strategy, which primarily benefits the land owners and does not consider environmental heterogeneity or biodiversity. It then identified the socially optimal harvest where both the direct effects on species abundance and indirect effects on landscape structure were considered. By doing this, the model considers the external impact of the individual land user on the heterogeneity of a whole landscape system. This is typically ignored in most private land use decisions. For example, a forester who replaces old natural forest with a monoculture changes the heterogeneity of the landscape and the biodiversity both in the area under his control and in the whole system but does not consider the impact on the whole system when making his decision.
If the impact of this decision on the system is identified then corrective measures can be applied. This model could help understand not only the impact of removing wild species and overharvesting, but also the impacts on environmental heterogeneity, which could be one of the most important, if unintended, drivers of biodiversity loss.
Source: Brock, W., Kinzig, A. & Perrings, C. (2010) Modelling the Economics of Biodiversity and Environmental Heterogeneity. Environmental and Resource Economics, 46(1): 43-58.
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