Avian abundance and communities in areas revegetated with exotic versus native plant species

Abstract

Degradation of ecosystems and introductions of invasive species pose a threat to global biodiversity. Ecosystem restoration and revegetation actions are important for amending habitat loss and for the protection of species of plants and animals. Iceland has the highest rate of soil erosion and desertification in Northern Europe and counteractions to erosion and revegetation measures have taken place for over a century. We studied the effect of revegetation on the density and composition of birds and invertebrate abundance in 26 survey areas comparing: a) unvegetated eroded areas, b) native heathlands restored on eroded land, and c) revegetation by the introduced and exotic Nootka lupin (Lupinus nootkatensis) on eroded land. Birds were counted on transects and invertebrates sampled with a sweep net. Both revegetation methods greatly increased the abundance of birds. The highest total numbers of invertebrates and birds were recorded on land revegetated with Nootka lupin. On average 31 birds km-2 were recorded on barren land, 337 on heathland and 627 in Nootka lupin. Bird species composition differed between the two revegetation methods. Restored heathland provided habitat for waders of internationally decreasing populations, whereas Nootka lupin stands harboured more common bird species. Golden Plover (Pluvialis apricaria) and Dunlin (Calidris alpina) were most common on restored heathland, while Snipe (Gallinago gallinago) and Meadow Pipit (Anthus pratensis) were most common in Nootka lupine. The abundance of birds was positively correlated with that of invertebrates. The abundance of different bird species differed by successional stage in each habitat. The study showed the generally positive effects of revegetation on animal biodiversity and also how different revegetation methods produce different trajectories of ecosystem development.