2,515 research outputs found
Redefining landscape structure for ecosystem services
No full textOur understanding of the effects of landscape structure on ecosystem services (ES) remains at a very early stage, despite a large body of literature on the effects of the composition and configuration of natural land cover on some ES. Here, I argue that a comprehensive understanding of the effects of landscape structure on ES requires us to reconsider what constitutes landscape structure for ES. Such reconsideration requires us to re-visit John Wiens’ idea that for biodiversity, a landscape and its structure are organism- and question- dependent and apply this idea to ES by redefining landscape structure for ES to include not only land cover, but also other social and biophysical drivers of ES. The underlying reason for this is that ES are products of coupled socio-ecological systems and therefore do not only depend on ecological processes and/or distributions of key species, but also on social and biophysical variables. As a result, for many ES, relevant landscape structure will not only include features traditionally considered by ecologists, such as natural land cover, but also the amount and configuration of social variables, such as land management systems and distributions of wealth and human populations. Obtaining a general understanding of how landscape structure affects ES is vital if we are to manage landscapes effectively to ensure sustainable supplies of ES now and into the future
Quantifying the road effect zone: threshold effects of a motorway on anuran populations in Ontario, Canada
No full textThe negative effect of roads on wildlife is recognized as a major contributor to the global biodiversity crisis, with anurans being among the most vulnerable groups overall. The “road-effect zone,” i.e., the extent of significant ecological effects from the edge of a road (Forman and Alexander 1998), has important management implications, but has never been quantified for anurans. In the first study of its kind, we measured the extent and type of relationship underlying the road-effect zones of a motorway with a high proportion of heavy-truck traffic, particularly at night (Highway 401) for anuran species richness and relative abundance. We surveyed 34 ponds located 68–3262 m from the edge of the motorway, and used piecewise and linear regressions to determine if road-effect zones were clearly delineated by ecological thresholds. We found road-effect zones of 250–1000 m delineated by ecological thresholds for four of seven species and species richness, and road-effect zones of well beyond 1000 m best described by linear regressions for two species. The negative effect of Highway 401 was unexpectedly strong for four of seven species suggest that, in addition to road mortality, very high nighttime truck traffic can actually lead to reduced use of breeding habitat near the motorway either by acting as a barrier to forest habitat on the other side of the highway and/or because of traffic noise. Our results show that most anurans are likely to have reduced abundances near motorways, but that both the extent of the effect of this type of road and the underlying relationship vary considerably between species. Furthermore, the noise and/or barrier effect of very high nighttime traffic volumes can lead to negative effects of motorways even on species that are relatively unaffected by direct road mortalit
Sub-optimal study design has major impacts on landscape-scale inference
No full textLandscape-scale processes (e.g. habitat loss) are major drivers of the global biodiversity crisis, but the complexity and size of landscapes makes study design at this scale difficult. However, the impact of statistical problems associated with sub-optimal study design on inferences drawn from landscape-scale studies is poorly understood. Here, we examine how three common statistical ‘pitfalls’ associated with sub-optimal study design – (1) using landscapes that overlap in space; (2) using only a portion of the potential range of the landscape predictor variable(s) of interest; (3) failing to account for correlations among landscape predictor variables – affect the inferred relationships between the abundances of six species of anurans and the amount of forest in the landscape using a large (n = 1141) empirical dataset from Wisconsin and Michigan, USA. We show that sub-optimal study design alone can be sufficient to cause a switch in the sign of the inferred relationship between a species response and landscape structure, and that using only a portion of the potential range of a predictor variable, and correlations between predictor variables, are particularly likely to affect inferences. Our results also provide the first evidence of a non-monotonic relationship between forest amount and gray treefrog abundance, and suggest that inconsistencies in the literature about the inferred relationships between anuran presence/abundance and forest amount in the Great Lakes basin are likely largely due to sampling design issues. Increased attention to study design is therefore necessary for the development of robust generalizations in landscape ecolog
Scale-dependency in drivers of outdoor recreation in England
No full text1. Managing landscapes for multiple, sometimes conflicting, objectives requires an understanding of the trade-offs and synergies between ecosystem services (ES). These trade-offs and synergies are often the result of drivers acting at different scales. Therefore, in order to understand trade-offs and synergies it is important that we understand the scale dependency in drivers of ES.2. Here, we examine scale dependencies in the drivers of outdoor recreation in England to better understand trade-offs between different aspects of this ES. We focus on outdoor recreation because it is culturally and economically important; it is the result of a range of social and biophysical attributes which vary at different scales; and proxies that are independent of these drivers exist. 3. First, we tested the hypothesis that a social media based proxy (photographs from Flickr) represents ‘destination’ recreation (e.g. day trips and overnight visits). We did so by comparing to a survey based proxy, which is known to represent ‘day-to-day’ recreation (e.g. dog walking, visiting local parks). Second, we examined the scale dependencies in the social and biophysical drivers of both types of outdoor recreation. 4. Flickr data were best explained by variables capturing supply of recreation; whereas the survey data were best explained by variables capturing demand for recreation. This confirms our hypothesis that Flickr data measure ‘destination’ recreation given that the survey data measure ‘day-to-day’ recreation. In both cases, the importance of demand variables increased with increasing spatial resolution. 5. Understanding what a proxy measures provides us with information about how to use it. We conclude that Flickr data may be useful to plan at broad scales, but that to plan for equitable day-to-day recreation, specially designed survey data may be more appropriate. Estimating the scale dependencies in drivers of outdoor recreation gets us a step closer to a mechanistic understanding of the social-ecological system. <br/
Effects of surrounding urbanization on non-native flora in small forest patches
No full textThe purpose of our study was to compare the number, proportion, and species composition of introduced plant species in forest patches situated within predominantly forested, agricultural, and urban landscapes. A previous study suggested that agricultural landscape context does not have a large effect on the proportion of introduced species in forest patches. Therefore, our main goal was to test the hypothesis that forest patches in an urban landscape context contain larger numbers and proportions of non-native plant species. We surveyed the vegetation in 44 small remnant forest fragments (3-7.5 ha) in the Ottawa region; 15 were situated within forested landscapes, 18 within agricultural landscapes, and 11 within urban landscapes. Forest fragments in urban landscapes had about 40% more introduced plant species and a 50% greater proportion of introduced plant species than fragments found in the other two types of landscape. There was no significant difference in the number or proportion of introduced species in forest fragments within forested vs. agricultural landscapes. However, the species composition of introduced species differed among the forest patches in the three landscape types. Our results support the hypothesis that urban and suburban areas are important foci for spread of introduced plant specie
The relative effects of road traffic and forest cover on anuran populations
No full textRoad traffic and the loss of forests are both known to have negative effects on anurans. However, the relative importance of these two predictors is poorly understood because for est cover in the landscape is usually negatively correlated with the density of roads and traffic. To evaluate the independent effects of traffic and forest cover, we selected 36 ponds near Ottawa, Canada, at the center of four landscape types: low forest/low traffic; low for est/high traffic; high forest/low traffic; and high forest/high traffic, where traffic and forest cover were measured within 100 - 2000 in of the edge of each pond. We surveyed all ponds in 2005 and re-surveyed a 23-pond subset in 2006. The negative association between species richness and traffic density was stronger (partial R-2=0.34; P <.001) than the positive asso ciation of species richness with forest cover (partial R-2=0.10; P >.05) in the landscape. Three of six common species showed stronger associations with traffic density than with forest cover - Bufo americanus, Rana pipiens, and Hyla versicolor; two species - Pseudacris cru cifer and Rana syluatica - showed stronger associations with forest cover than with traffic; while Raria clamitans showed similar associations with traffic and forest cover. Our results show that the overall negative effect of traffic on anuran populations in northeastern North America is at least as great as the negative effect of deforestation, and also that the relative effects of these two predictors on anuran abundance vary between specie
Accessible habitat: an improved measure of the effects of habitat loss and roads on wildlife populations
No full textHabitat loss is known to be the main cause of the current global decline in biodiversity, and roads are thought to affect the persistence of many species by restricting movement between habitat patches. However, measuring the effects of roads and habitat loss separately means that the configuration of habitat relative to roads is not considered. We present a new measure of the combined effects of roads and habitat amount: accessible habitat. We define accessible habitat as the amount of habitat that can be reached from a focal habitat patch without crossing a road, and make available a GIS tool to calculate accessible habitat. We hypothesize that accessible habitat will be the best predictor of the effects of habitat loss and roads for any species for which roads are a major barrier to movement. We conducted a case study of the utility of the accessible habitat concept using a data set of anuran species richness from 27 ponds near a motorway. We defined habitat as forest in this example. We found that accessible habitat was not only a better predictor of species richness than total habitat in the landscape or distance to the motorway, but also that by failing to consider accessible habitat we would have incorrectly concluded that there was no effect of habitat amount on species richnes
Vulnerability of ecosystems to climate change moderated by habitat intactness
No full textThe combined effects of climate change and habitat loss represent a major threat to species and ecosystems around the world. Here, we analyse the vulnerability of ecosystems to climate change based on current levels of habitat intactness and vulnerability to biome shifts, using multiple measures of habitat intactness at two spatial scales. We show that the global extent of refugia depends highly on the definition of habitat intactness and spatial scale of the analysis of intactness. Globally, 28% of terrestrial vegetated area can be considered refugia if all natural vegetated land cover is considered. This, however, drops to 17% if only areas that are at least 50% wilderness at a scale of 48 × 48 km are considered and to 10% if only areas that are at least 50% wilderness at a scale of 4.8 × 4.8 km are considered. Our results suggest that, in regions where relatively large, intact wilderness areas remain (e.g. Africa, Australia, boreal regions, South America), conservation of the remaining large-scale refugia is the priority. In human-dominated landscapes, (e.g. most of Europe, much of North America and Southeast Asia), focusing on finer scale refugia is a priority because large-scale wilderness refugia simply no longer exist. Action to conserve such refugia is particularly urgent since only 1 to 2% of global terrestrial vegetated area is classified as refugia and at least 50% covered by the global protected area network
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