Aim Using New Zealand land snails as a case study, we evaluated recent spatial modelling approaches for the analysis of diversity in species-rich invertebrate groups. Applications and prospects for improved conservation assessment were investigated.Location New Zealand.Methods The study used a spatially extensive and taxonomically comprehensive, plot-based dataset on community structure in New Zealand land snails. Generalized regression analysis and spatial prediction (GRASP) was used to model and predict species richness as a function of environmental variables (including aspects of climate, soils and vegetation). Generalized dissimilarity modelling (GDM) was used to model turnover in species composition in relation to environmental and geographical distances, and to assess community similarity and the representativeness of the reserve network.Results Observed land snail richness in 20 · 20 m plots ranged from 1 to 74 (mean 17.5). The GRASP model explained a modest 27% of the variation in richness. The GDM model explained 57% of the variation in species turnover and indicated approximately equal amounts related to environmental (Cody's beta diversity) and geographical distance (Cody's gamma diversity). Temperature and moisture were the most important environmental variables. Results indicate that snail distributions are not only sorted by environment but are also strongly influenced by historical effects consistent with those expected of poorly dispersing taxa that have persisted in refugia during past climatic change. The GDM model enabled spatial classifications of snail communities, highlighting diverse communities in heterogeneous regions, such as the South Island mountains, and also enabled continuous depictions of community similarity and adequacy of New Zealand's protected natural areas network.Main conclusions The GRASP and GDM analyses allowed us to model and depict spatial patterns of diversity in land snail communities involving 845 species, and produce community classifications and estimates of community similarity. These tools advance conservation assessment in species-rich groups, but require further conceptual and methodological development.

Invasions by alien pest species contribute heavily to global biodiversity decline, with invasive mammals having some of the greatest impacts on endemic biota. Pest management within ecological restorations is therefore critical for conserving threatened biota. Coordinating restoration efforts at global scale requires evidence of the relative efficacy of different pest-managed restoration approaches ("regimes") for enhancing biodiversity. Our national meta-analysis of 447 biodiversity responses across 16 ecological restorations quantifies significant benefits for biodiversity over two decades and multiple trophic levels, and across a spectrum of invasive mammal suppression-to-eradication regimes. Deeply endemic species had the strongest responses to pest control compared with recent native or introduced biota. Using this information, we predict levels of pest suppression required to confer biodiversity benefits, to guide future management strategies. Our findings provide new evidence that invasive pest control is an effective approach to ecological restoration, to aid decision-makers in setting objectives and making targeted investments.

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We measured the net progress of land reform in achieving a national policy goal for biodiversity conservation in the context of ongoing clearing of native vegetation and additions of land to a highly nonrepresentative (residual) reserve network, interior South Island, New Zealand. We used systematic conservation-planning approaches to develop a spatially explicit index of risk of biodiversity loss (RBL). The index incorporated information from national data sets that describe New Zealand's remaining indigenous land cover, legal protection, and land environments and modeled risk to biodiversity on the basis of stated assumptions about the effects of past habitat loss and legal protection. The index identified irreplaceable and vulnerable native habitats in lowland environments as the most at risk of biodiversity loss, and risk was correlated with the density of threatened plant records. To measure achievement, we used changes in the index that reflected gains made and opportunity costs incurred by legal protection and privatization. Application of the index to measure the difference made by land reform showed it had caused a net increase in the risk of biodiversity loss because most land vulnerable to habitat modification and rich in threatened plant species was privatized and land at least risk of biodiversity loss was protected. The application revealed that new high-elevation reserves did little to mitigate biodiversity decline, that privatization of low-elevation land further jeopardized the most vulnerable biodiversity in lowland native habitats, and that outcomes of land reform for biodiversity deteriorated over time. Further development of robust achievement measures is needed to encourage more accountable biodiversity conservation decisions.

Seven introduced deer taxa are present in New Zealand and there is interest in the dynamics of these populations. Estimating the abundance of deer is problematic, but faecal pellet counts (an index of abundance) have been conducted on New Zealand's public conservation land since the 1950s. We compiled faecal pellet count data from published and unpublished sources, and used the most common data type (presenceÁabsence of pellets in plots along transects) to investigate decadal changes in the relative abundances of deer at the national, island (North and South) and Department of Conservation conservancy spatial scales. A quadratic model with different trends for each conservancy best explained the pellet frequency data for the period 1952Á2010: pellet frequencies were highest during the 1950sÁ1970s and then declined to minima in the 1980s and 1990s and then increased in the 2000s. The decline in pellet frequencies was likely caused by increasing commercial deer harvesting, and the recent increases in pellet frequencies in several conservancies are likely a consequence of reduced commercial harvesting. The key limitations of faecal pellet count data collected in New Zealand (i.e. spatial and temporal variability, and that only summary statistics are often available) are discussed.