Quantifying the biodiversity values of reforestation: perspectives, design issues and outcomes in Australian rainforest landscapes

Abstract

Following two centuries of land clearing, the past two decades have seen growing efforts to reestablish forest on formerly-cleared sites. While the immediate goals of reforestation vary, there is also a widespread expectation that one of its effects will be an improvement in "biodiversity value". However, agreed standards concerning how this can be measured, and against what benchmarks it should be judged, are lacking. This paper describes a study of biodiversity development in different types of rainforest reforestation in tropical and subtropical eastern Australia. It provides information on the responses of rainforest fauna and also discusses key issues of survey design and methodology that, if ignored, may limit the effectiveness of monitoring programs. The nature of rainforest, its history within Australia, and its role as fauna habitat are briefly reviewed. Modern deforestation and human land use, and various reforestation pathways (including regrowth, timber plantation, and ecological restoration projects) are described. Then, design principles, biodiversity measurements, and issues relating to their choice are discussed. These include: spatial scale; site selection and replication in relation to environmental variation; reference sites; the array of potentially measurable biotic and process variables, and spatio-temporal measurement scales. Finally we explore analytical options and present selected findings, using univariate and multivariate approaches, and comparing simple species richness, functional groupings, and analyses of taxonomic composition. Rainforest biodiversity value is defined as the development of a rainforest-like set of biota and ecological processes. Reforested sites were generally intermediate between pasture and rainforest reference sites in the measured components of rainforest biodiversity value. Many components had been rapidly (by around 10 years) acquired by ecological restoration sites, although it is clear that some components will take decades or longer to develop. The results also show: (1) the existence of production/ biodiversity trade-offs, in that sites managed for timber production acquired less biodiversity value than those planted for ecological restoration; (2) moderate correspondence across different indicator taxa when they are analysed for assemblage composition; (3) very little agreement among indicator taxa when overall richness is used; (4) a likelihood of important landscape and context effects. Long-term conservation of rainforest fauna will require rainforest restoration over substantial areas of currently denuded land. However, although rainforest restoration may often show reasonable success, it should not be viewed as an alternative to conserving existing remnants and advanced regrowth.

Responses of ground-active beetle assemblages to different styles of reforestation on cleared rainforest land

“…EVorts to re-establish tree cover to land previously cleared of rainforest are relatively new (Janzen 1988;Parotta et al 1997;Catterall et al 2004) and thus their ability to sustain rainforest biota and potentially alleviate some of the deleterious eVects of forest degradation are largely unknown and untested.…”

“…DiVerent pathways for restoring forest cover in rainforest landscapes include un-managed regrowth, monocultures of plantation timber, and species-rich ecological restoration plantings (Lamb et al 1997;Erskine 2002;Kanowski et al 2003;Catterall et al 2004). Ecological restoration plantings are diverse and dense plantings of rainforest trees aimed at recreating rainforest.…”

Saving rainforests in the South Pacific: challenges in ex situ conservation

“…On-ground conservation efforts have been successful in some areas where broad scale clearing has largely ceased, such as in the tropical and subtropical rainforests of Australia (Catterall et al 2004), but have been difficult to implement in other areas of the South Pacific (Keppel et al 2012). Secondary rainforestsrainforests that develop on previously cleared land or primary rainforest that has been partially degraded -can have great conservation value but their diversity is dependent on the availability of propagules and agents to disperse them (Putz and Romero 2014).…”

Climate change, Variability and Conservation impacts in Australia.

“…This will provide further incentives for landholders to fund (or sell or lease their land for) long-term reforestation schemes (Walsh 1999). Reforestation not only sequesters carbon but reduces recurrent wind and water erosion and reverses the salinization of land and water resources, with positive benefits for industry and biodiversity (Catterall et al 2004, Harper et al 2007. Furthermore, a price on carbon should provide a market-driven means to promote the development of a habitat network across private lands, with substantial biodiversity and connectivity gains ).…”