Managing trade-offs in landscape restoration and revegetation projects

Landscape restoration projects often have multiple and disparate conservation, resource enhancement and sometimes economic objectives, since projects that seek to meet more than one objective tend to be viewed more positively by funding agencies and the community. The degree to which there are tradeoffs among desired objectives is an important variable for decision-makers, yet this is rarely explicitly considered. In particular, the existence of ecological thresholds has important implications for decision-making at both the project level and the regional level. We develop a model of the possibilities and choices for an agency seeking to achieve two environmental objectives in a region through revegetation of a number of sites. A graphical model of the production possibilities sets for a single revegetation project is developed and different tradeoff relationships are discussed and illustrated. Then the model is used to demonstrate the possibilities for managing all such projects within a region. We show that where there are thresholds in the tradeoff relationship between two objectives, specialization (single- or dominant- objective projects) should be considered. This is illustrated using a case study in which revegetation is used to meet avian biodiversity and salinity mitigation objectives. We conclude that where there are sufficient scientific data, explicit consideration of different types of tradeoffs can assist in making decisions about the most efficient mix and type of projects to better achieve a range of objectives within a region

Temporal variation in bird assemblages: how representative is a one-year snapshot?

Bird assemblages generally are no longer regarded as stable entities, but rather as fluctuating in response to many factors. Australia’s highly variable climate is likely to result in a high degree of dynamism in its bird assemblages, yet few studies have investigated variation on an inter-annual temporal scale. We compared two year-long samples of the bird assemblages of a series of highly fragmented buloke Allocasuarina luehmannii (Casuarinaceae)woodland remnants in south-eastern Australia, the first sample taken in 1994–1995 and the second in 2001–2002. Bird densities were almost three times higher in the second period than in the first. Mean species richness also was significantly higher. Species richness of each individual site was unrelated between the two years. Minimum species turnover was 63% and was higher, on average, for migratory and nomadic than for sedentary species. Therefore, site-level bird assemblage composition was markedly different between the two survey periods and, on average, the assemblage composition of each site bore greater resemblance to those of other sites in the same year than to that of the same site in the other survey period. Most species changed substantially in their distribution among remnants between the two periods. The change in distribution of most species did not differ significantly from that expected if the species had redistributed at random among the sites. This suggests that although the remnant vegetation of the area is highly fragmented with minimal interpatch connectivity, bird movements among remnants must be relatively frequent. Interannual variability in Australian bird assemblages may be higher than is commonly recognized. In such dynamic systems, we must be cautious when extrapolating from the findings of short-term studies to longer temporal scales, especially in relation to conservation management. A greater understanding of the processes driving distributional patterns is likely to enable better predictions of species’ responses to habitat change

Continent-scale pattern in temporal dynamics of avian assemblages

A common method of characterizing the bird assemblages of sites in landscape ecological research is to conduct a series of snapshot-type surveys, often over less than one year (Maron et al. 2005). However, highly mobile taxa such as birds show substantial interannual variability in species richness and community composition (e.g. Holmes et al. 1986), and this may have implications for the veracity of snapshot-derived patterns. The environmental correlates of inter-annual variability in bird assemblages are not well known, although it seems likely that more climatically stable regions support less dynamic avian assemblages (Jarvinen 1979). We conducted a continent-scale study to investigate associations between environmental factors and annual bird assemblage turnover rates in Australia. Correlates of inter-annual bird assemblage variability have rarely been investigated at this scale as long-term data from across a broad area are required. However, the availability of long-term, large-scale databases from volunteer-based monitoring initiatives provides opportunities for comparisons across large areas. For example, data from the North American Breeding Bird Survey revealed increased annual turnover in landscapes with smaller forest patches (Boulinier et al. 2001)

Saving our Species: Guidelines for estimating a evaluating species' response to management

Provides guidance to species' managers within the Saving our Species program on how to estimate a species’ response to management for the purpose of setting targets for adaptive management. These guidelines were developed through a series of end user workshops and are designed as a\ua0tool for using expert judgement in the absence of quantitative data. This is a acheived using a combination of conceptual modelling\ua0and a structured elicitiation protocol. This work was commissioned by the NSW Department on Planning Industry and the Environment (formerly Office of Environment and Heritage) and carried out in conjunction with the National Environmental Science Program Threatened Species Recovery Hub

Despotic, high-impact species and the subcontinental scale control of avian assemblage structure

Some species have disproportionate influence on assemblage structure, given their numbers or biomass. Most examples of such "strong interactors'' come from small-scale experiments or from observations of the effects of invasive species. There is evidence that entire avian assemblages in open woodlands can be influenced strongly by individual species over very large areas in eastern Australia, with small-bodied species (2000 km). A series of linked Bayesian models was used to identify large-bodied (>= 50 g) bird species that were associated with changes in occurrence and abundance of small-bodied species. One native species, the Noisy Miner (Manorina melanocephala; family Meliphagidae), was objectively identified as the sole large-bodied species having similar detrimental effects in all districts, depressing occurrence of 57 of 71 small-bodied species. Adverse effects on abundances of small-bodied species were profound when the Noisy Miner occurred with mean site abundances >= 1.6 birds/2 ha. The Noisy Miner may be the first species to have been shown to influence whole-of-avifauna assemblage structure through despotic aggressiveness over subcontinental scales. These substantial shifts in occurrence rates and abundances of small-bodied species flow on to alter species abundance distributions of entire assemblages over much of eastern Australia

Improving averted loss estimates for better biodiversity outcomes from offset exchanges

Biodiversity offsetting aims to achieve at least ‘no net loss’ of biodiversity by fully compensating for residual development-induced biodiversity losses after the mitigation hierarchy (avoid, minimise, remediate) has been applied. Actions used to generate offsets can include securing protection, maintaining condition, or enhancing condition of targeted biodiversity at an offset site. Protection and maintenance actions aim to prevent future loss of biodiversity, so such offsets are referred to as ‘averted loss’ offsets. However, the benefits of such approaches can be highly uncertain and opaque, because assumptions about the change in likelihood of loss due to the offset are often implicit. As a result, the gain generated by averting losses can be intentionally or inadvertently overestimated, leading to offset outcomes that are insufficient for achieving no net loss of biodiversity. We present a method and decision tree to guide consistent and credible estimation of the likelihood of loss of a proposed offset site with and without protection, for use when calculating the amount of benefit associated with the ‘protection’ component of averted loss offsets. In circumstances such as when a jurisdictional offset policy applies to most impacts, plausible estimates of averted loss can be very low. Averting further loss of biodiversity is desirable, and averted loss offsets can be a valid approach for generating tangible gains. However, overestimation of averted loss benefits poses a major risk to biodiversity

Land clearing in Queensland triples after policy ping pong

[Extract] In 2013, a group of 26 senior scientists in Queensland (including ourselves) expressed serious concern that proposed changes to vegetation protection laws would mean a return to large-scale land clearing. The loss of these protections followed a Ministerial announcement in early 2012 that investigations into and prosecutions of illegal clearing would be halted

To reduce fire risk and meet climate targets, over 300 scientists call for stronger land clearing laws

Australia’s high rates of forest loss and weakening land clearing laws are increasing bushfire risk, and undermining our ability to meet national targets aimed at curbing climate change. This dire situation is why we are among the more than 300 scientists and practitioners who have signed a declaration calling for governments to restore, or better strengthen regulations to protect native vegetation