Matthew G. E. Mitchell

Linking landscape connectivity and ecosystem service provision: current knowledge and research gaps

Human activities are rapidly changing ecosystems, landscapes and ecosystem service provision, yet there remain significant gaps in our understanding of the spatial ecology of ecosystem services. These gaps hinder our ability to manage landscapes effectively for multiple ecosystem services. In particular, we do not fully understand how changes in landscape connectivity affect ecosystem service provision, despite theory suggesting that connectivity is important. Here, we perform a semi-quantitative review of the literature that investigates how landscape connectivity affects the provision of specific ecosystem services. The vast majority of studies, including reviews, models, and field studies, suggest that decreased connectivity will have negative effects on ecosystem service provision. However, only 15 studies provided empirical evidence of these effects. Average effect sizes from these 15 studies suggest negative effects of connectivity loss on pollination and pest regulation. We identify a number of significant gaps in the connectivity-ecosystem services literature, including: a lack of multiple service studies, which precludes identification of trade-offs between services as connectivity changes; few studies that directly measure organism movement and its effects on ecosystem services; and few empirical studies that investigate the importance of abiotic flows on service provision. We propose that future research should aim to understand how different aspects of connectivity affect ecosystem service provision; which services are most influenced by connectivity; and how connectivity influences how humans access and benefit from ecosystem services. Studies that answer these questions will advance our understanding of connectivity-ecosystem service provision relationships and allow for better ecosystem and landscape management and restoration.

Reframing landscape fragmentation's effects on ecosystem services

Landscape structure and fragmentation have important effects on ecosystem services, with a common assumption being that fragmentation reduces service provision. This is based on fragmentations expected effects on ecosystem service supply, but ignores how fragmentation influences the flow of services to people. Here we develop a new conceptual framework that explicitly considers the links between landscape fragmentation, the supply of services, and the flow of services to people. We argue that fragmentations effects on ecosystem service flow can be positive or negative, and use our framework to construct testable hypotheses about the effects of fragmentation on final ecosystem service provision. Empirical efforts to apply and test this framework are critical to improving landscape management for multiple ecosystem services.

Forest fragments modulate the provision of multiple ecosystem services

Agricultural landscapes provide the essential ecosystem service of food to growing human populations; at the same time, agricultural expansion to increase crop production results in forest fragmentation, degrading many other forest-dependent ecosystem services. However, surprisingly little is known about the role that forest fragments play in the provision of ecosystem services and how fragmentation affects landscape multifunctionality at scales relevant to land management decisions. We measured the provision of six ecosystem services (crop production, pest regulation, decomposition, carbon storage, soil fertility and water quality regulation) in soya bean fields at different distances from adjacent forest fragments that differed in isolation and size across an agricultural landscape in Quebec, Canada. We observed significant effects of distance-from-forest, fragment isolation and fragment size on crop production, insect pest regulation, and decomposition. Distance-from-forest and fragment isolation had unique influences on service provision for each of the ecosystem services we measured. For example, pest regulation was maximized adjacent to forest fragments, while crop production was maximized at intermediate distances-from-forest. As a consequence, landscape multifunctionality depended on landscape heterogeneity: the range of field and forest fragment types present. We also observed strong negative and positive relationships between ecosystem services that were more prevalent at greater distances-from-forest. Synthesis and applications. Our study is one of the first to empirically measure and model the effects of forest fragments on the simultaneous provision of multiple ecosystem services in an agro-ecosystem at the landscape and field scales relevant to landowners and managers. Our results demonstrate that forest fragments, irrespective of their size, can affect the provision of multiple ecosystem services in surrounding fields, but that this effect is mediated by fragment isolation across the landscape. Our results also suggest that managing habitat fragmentation and landscape structure will improve our ability to optimize ecosystem service provision and create multifunctional agricultural landscapes. Our study is one of the first to empirically measure and model the effects of forest fragments on the simultaneous provision of multiple ecosystem services in an agro-ecosystem at the landscape and field scales relevant to landowners and managers. Our results demonstrate that forest fragments, irrespective of their size, can affect the provision of multiple ecosystem services in surrounding fields, but that this effect is mediated by fragment isolation across the landscape. Our results also suggest that managing habitat fragmentation and landscape structure will improve our ability to optimize ecosystem service provision and create multifunctional agricultural landscapes.

The Monteregie Connection: linking landscapes, biodiversity, and ecosystem services to improve decision making

To maximize specific ecosystem services (ES) such as food production, people alter landscape structure, i.e., the types of ecosystems present, their relative proportions, and their spatial arrangement across landscapes. This can have significant, and sometimes unexpected, effects on biodiversity and ES. Communities need information about how land/use activities and changes to landscape structure are likely to affect biodiversity and ES, but current scientific understanding of these effects is incomplete. The Monteregie Connection (MC) project has used the rapidly suburbanizing agricultural Monteregien landscape just east of Montreal, Quebec, Canada, to investigate how current and historic landscape structure influences ES provision. Our results highlight the importance of forest connectivity and functional diversity on ES provision, and show that ES provision can vary significantly even within single land-use types in response to changes in landscape structure. Our historical analysis reveals that levels of ES provision, as well as relationships among individual ES, can change dramatically through time. We are using these results to build quantitative ES-landscape structure models to assess four future landscape scenarios for the region: Periurban Development, Demand for Energy, Whole-System Crisis, and Green Development. These scenarios integrate empirical and historical data on ES provision with local stakeholder input about global and local social and ecological drivers to explore how land-use decisions could affect ES provision and human well-being across the region to the year 2045. By integrating empirical data, quantitative models, and scenarios we have achieved the central goals of the MC project: (1) increasing understanding of the effects of landscape structure on biodiversity and ES provision, (2) effectively linking this knowledge to decision making to better manage for biodiversity and ES, and (3) creating a vision for a more sustainable social-ecological system in the region.

Plant interactions are unimportant in a subarctic-alpine plant community

We investigated whether plant interaction intensity in a subarctic-alpine meadow is important for determining community structure and species abundance. Using two common species as phytometers, we measured interaction intensity using a neighbor removal approach. Eight biotic and abiotic variables known to influence species abundance and community structure were measured, with regression trees used to examine how plant interactions and the biotic and abiotic variables were related to species evenness, richness, and phytometer spatial cover. A range of interactions was present, with both strong competition and facilitation present over small-scale abiotic and biotic gradients. Despite the variation in interaction intensity, it was generally unrelated to either community structure or phytometer cover. In other words, plant interactions were intense in many cases but were not important to community structure. This may be due to the prevalence of clonal species in this system and the influence of previous years interactions on plant survival and patterns of community structure. These results also suggest how conflicting theories of the role of competition in unproductive environments may be resolved. Our findings suggest that plant interactions may be intense in reducing individual growth, while simultaneously not important in the context of community structure. Plant interactions need to be viewed and tested relative to other factors and stresses to accurately evaluate their importance in plant communities, with continued differentiation between the intensity of plant interactions and their relative importance in communities.

Variability in ecosystem service measurement: a pollination service case study

Research quantifying ecosystem services (ES) - collectively, the benefits that society obtains from ecosystems -is rapidly increasing. Despite the seemingly straightforward definition, a wide varie ...

Strong and nonlinear effects of fragmentation on ecosystem service provision at multiple scales

Human actions, such as converting natural land cover to agricultural or urban land, result in the loss and fragmentation of natural habitat, with important consequences for the provision of ecosystem services. Such habitat loss is especially important for services that are supplied by fragments of natural land cover and that depend on flows of organisms, matter, or people across the landscape to produce benefits, such as pollination, pest regulation, recreation and cultural services. However, our quantitative knowledge about precisely how different patterns of landscape fragmentation might affect the provision of these types of services is limited. We used a simple, spatially explicit model to evaluate the potential impact of natural land cover loss and fragmentation on the provision of hypothetical ecosystem services. Based on current literature, we assumed that fragments of natural land cover provide ecosystem services to the area surrounding them in a distance-dependent manner such that ecosystem service flow depended on proximity to fragments. We modeled seven different patterns of natural land cover loss across landscapes that varied in the overall level of landscape fragmentation. Our model predicts that natural land cover loss will have strong and unimodal effects on ecosystem service provision, with clear thresholds indicating rapid loss of service provision beyond critical levels of natural land cover loss. It also predicts the presence of a tradeoff between maximizing ecosystem service provision and conserving natural land cover, and a mismatch between ecosystem service provision at landscape versus finer spatial scales. Importantly, the pattern of landscape fragmentation mitigated or intensified these tradeoffs and mismatches. Our model suggests that managing patterns of natural land cover loss and fragmentation could help influence the provision of multiple ecosystem services and manage tradeoffs and synergies between services across different human-dominated landscapes.

Using high-resolution LiDAR data to quantify the three-dimensional structure of vegetation in urban green space

The spatial arrangement and vertical structure of vegetation in urban green spaces are key factors in determining the types of benefits that urban parks provide to people. This includes opportunities for recreation, spiritual fulfilment and biodiversity conservation. However, there has been little consideration of how the fine-scale spatial and vertical structure of vegetation is distributed in urban parks, primarily due to limitations in methods for doing so. We addressed this gap by developing a method using Light Detection and Ranging (LiDAR) data to map, at a fine resolution, tree cover, vegetation spatial arrangement, and vegetation vertical structure. We then applied this method to urban parks in Brisbane, Australia. We found that parks varied mainly in their amount of tree cover and its spatial arrangement, but also in vegetation vertical structure. Interestingly, the vertical structure of vegetation was largely independent of its cover and spatial arrangement. This suggests that vertical structure may be being managed independently to tree cover to provide different benefits across urban parks with different levels of tree cover. Finally, we were able to classify parks into three distinct classes that explicitly account for both the spatial and vertical structure of tree cover. Our approach for mapping the three-dimensional vegetation structure of urban green space provides a much more nuanced and functional description of urban parks than has previously been possible. Future research is now needed to quantify the relationships between vegetation structure and the actual benefits people derive from urban green space.

Landscape structure influences urban vegetation vertical structure

Summary Vegetation vertical structure is important for biodiversity and ecosystem service provision. In cities, however, while variation in the spatial extent and distribution of vegetation has been widely investigated, vertical vegetation structure and its potential drivers have not. Understanding how vegetation vertical structure varies across cities and identifying the potential drivers of this variation will improve the management of urban vegetation for biodiversity and ecosystem services. We used light detection and ranging (LiDAR) data to quantify the vertical structure of vegetation across Brisbane, Australia, at 1-km2 and 1-ha spatial scales and investigated how this structure varied in response to biophysical, socioeconomic, urban form and landscape structure variables. Using model selection techniques, we found that landscape structure variables related to tree cover (tree cover extent and spatial configuration) best explained the vegetation vertical structure at both spatial scales. Biophysical and urban form variables were also important, but only in combination with landscape structure. Mean vegetation vertical complexity, foliage projective cover and canopy height at a site all decreased as the treed proportion of the surrounding urban landscape decreased. In general, these vertical structure variables also increased where patches of vegetation were clustered together spatially. Synthesis and applications. Using light detection and ranging (LiDAR) data and model selection techniques, we show that the extent and vertical structure of urban vegetation are not independent and that reduced extent and increased fragmentation of urban vegetation are associated with simplification of its vertical structure. If common, this relationship means that managing urban vegetation for biodiversity and ecosystem services should not focus solely on the amount of tree cover or green space present across cities, but also on identifying where interventions to improve vegetation vertical complexity are required. Our study provides important insights into where these locations may be in cities.

Identification of fine scale and landscape scale drivers of urban aboveground carbon stocks using high-resolution modeling and mapping

Urban areas are sources of land use change and CO2 emissions that contribute to global climate change. Despite this, assessments of urban vegetation carbon stocks often fail to identify important landscape-scale drivers of variation in urban carbon, especially the potential effects of landscape structure variables at different spatial scales. We combined field measurements with Light Detection And Ranging (LiDAR) data to build high-resolution models of woody plant aboveground carbon across the urban portion of Brisbane, Australia, and then identified landscape scale drivers of these carbon stocks. First, we used LiDAR data to quantify the extent and vertical structure of vegetation across the city at high resolution (5×5m). Next, we paired this data with aboveground carbon measurements at 219 sites to create boosted regression tree models and map aboveground carbon across the city. We then used these maps to determine how spatial variation in land cover/land use and landscape structure affects these carbon stocks. Foliage densities above 5m height, tree canopy height, and the presence of ground openings had the strongest relationships with aboveground carbon. Using these fine-scale relationships, we estimate that 2.2±0.4 TgC are stored aboveground in the urban portion of Brisbane, with mean densities of 32.6±5.8MgCha-1 calculated across the entire urban land area, and 110.9±19.7MgCha-1 calculated within treed areas. Predicted carbon densities within treed areas showed strong positive relationships with the proportion of surrounding tree cover and how clumped that tree cover was at both 1km2 and 1ha resolutions. Our models predict that even dense urban areas with low tree cover can have high carbon densities at fine scales. We conclude that actions and policies aimed at increasing urban carbon should focus on those areas where urban tree cover is most fragmented.