The ecological consequences of habitat loss and fragmentation in New Zealand and Australia

Extensive loss and subdivision of Austral habitats has shaped the contemporary landscape and caused concomitant impacts on the region’s flora and fauna. This chapter draws on the scientific literature to explore the ecological changes brought about by the loss and fragmentation of indigenous habitats in New Zealand and Australia. We explore what it means for a habitat to become fragmented; and investigate how the rate and pattern of this phenomenon sculpts these landscapes. Inevitably, habitat changes on this scale have a pronounced impact on the physical and biotic conditions within remaining fragments. These effects are experienced from the scale of the gene right up to the diversity of species; impacting not only the individual but the interaction between individuals; modifying not only the organism’s immediate environment but their ability to disperse between patches; and affecting not only the organisms themselves but the ecological services they provide. Moreover, introduced species confound the impact of land-use change, and play an integral role influencing organisms in fragmented landscapes, so we go on to consider the interactions between these drivers. To conclude, this chapter reviews potential approaches for mitigating the impact of habitat fragmentation in order to conserve New Zealand and Australia’s unique biodiversity. Introduction Habitat fragmentation is an umbrella term used to describe a variety of inter-correlated patterns and processes (Ewers and Didham, 2007). It is sometimes considered the ‘lesser brother’ of habitat loss, though it seldom occurs without destruction of natural habitats. Fragmentation refers to the division of continuous habitat into small disconnected patches that are often altered in shape and isolated from each other by a matrix of dissimilar habitat (Collinge, 1996). Worldwide, habitat fragmentation has become the single largest topic of research in conservation biology (Fazey et al., 2005), and habitat loss has been recognised as the most immediate threat to global biodiversity (Wilson, 1992). Empirical studies identify five key consequences of habitat fragmentation that impact biodiversity: patch area, edge effects, isolation, fragment shape and matrix influences (Ewers and Didham, 2006). These attributes directly and indirectly explain the biota that persists within habitat remnants. Here, we review literature on the ecological consequences of habitat loss and fragmentation that are relevant to New Zealand and Australia. This chapter is by no means an exhaustive review of habitat fragmentation studies in the two countries, but rather it provides an overview of how habitat fragmentation has impacted the ecology of this region.