Regional boreal biodiversity peaks at intermediate human disturbance

• Published in: Nature communications 2012, Vol.3 (1), p.1142-1142, Article 1142
• Main Authors: Mayor, S.J., Cahill, J.F., He, F., Sólymos, P., Boutin, S.
• Format: Article
• Language: English
• Subjects: 631/158/670; 631/449/2668; Alberta; Biodiversity; Geography; Human Activities; Humanities and Social Sciences; Humans; multidisciplinary; Science; Science (multidisciplinary); Species Specificity; Trees - growth & development
• ISSN: 2041-1723; 2041-1723
• DOI: 10.1038/ncomms2145

The worldwide biodiversity crisis has intensified the need to better understand how biodiversity and human disturbance are related. The 'intermediate disturbance hypothesis' suggests that disturbance regimes generate predictable non-linear patterns in species richness. Evidence often contradicts intermediate disturbance hypothesis at small scales, and is generally lacking at large regional scales. Here, we present the largest extent study of human impacts on boreal plant biodiversity to date. Disturbance extent ranged from 0 to 100% disturbed in vascular plant communities, varying from intact forest to agricultural fields, forestry cut blocks and oil sands. We show for the first time that across a broad region species richness peaked in communities with intermediate anthropogenic disturbance, as predicted by intermediate disturbance hypothesis, even when accounting for many environmental covariates. Intermediate disturbance hypothesis was consistently supported across trees, shrubs, forbs and grasses, with temporary and perpetual disturbances. However, only native species fit this pattern; exotic species richness increased linearly with disturbance. Human influence on an ecosystem generates a predictable pattern in biodiversity. In a study of boreal plant communities, Mayor et al. show that the species richness of native vascular plants fits the predicted hump-shaped relationship to human disturbance, reaching a maximum when half of the landscape is disturbed.