Browsing by Author "Siriwardena, Gavin M."
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Item Open Access A bird's eye view: using circuit theory to study urban landscape connectivity for birds(Springer, 2017-06-28) Grafius, Darren Ronald; Corstanje, Ronald; Siriwardena, Gavin M.; Plummer, Kate E.; Harris, Jim A.Context Connectivity is fundamental to understanding how landscape form influences ecological function. However, uncertainties persist due to the difficulty and expense of gathering empirical data to drive or to validate connectivity models, especially in urban areas, where relationships are multifaceted and the habitat matrix cannot be considered to be binary. Objectives This research used circuit theory to model urban bird flows (i.e. ‘current’), and compared results to observed abundance. The aims were to explore the ability of this approach to predict wildlife flows and to test relationships between modelled connectivity and variation in abundance. Methods Circuitscape was used to model functional connectivity in Bedford, Luton/Dunstable, and Milton Keynes, UK, for great tits (Parus major) and blue tits (Cyanistes caeruleus), drawing parameters from published studies of woodland bird flows in urban environments. Model performance was then tested against observed abundance data. Results Modelled current showed a weak yet positive agreement with combined abundance for P. major and C. caeruleus. Weaker correlations were found for other woodland species, suggesting the approach may be expandable if re-parameterised. Conclusions Trees provide suitable habitat for urban woodland bird species, but their location in large, contiguous patches and corridors along barriers also facilitates connectivity networks throughout the urban matrix. Urban connectivity studies are well-served by the advantages of circuit theory approaches, and benefit from the empirical study of wildlife flows in these landscapes to parameterise this type of modelling more explicitly. Such results can prove informative and beneficial in designing urban green space and new developments.Item Open Access Ecological connectivity networks in rapidly expanding cities(Elsevier, 2017-06-23) Nor, Amal Najihah Muhamad; Corstanje, Ronald; Harris, Jim A.; Grafius, Darren R.; Siriwardena, Gavin M.Urban expansion increases fragmentation of the landscape. In effect, fragmentation decreases connectivity, causes green space loss and impacts upon the ecology and function of green space. Restoration of the functionality of green space often requires restoring the ecological connectivity of this green space within the city matrix. However, identifying ecological corridors that integrate different structural and functional connectivity of green space remains vague. Assessing connectivity for developing an ecological network by using efficient models is essential to improve these networks under rapid urban expansion. This paper presents a novel methodological approach to assess and model connectivity for the Eurasian tree sparrow (Passer montanus) and Yellow-vented bulbul (Pycnonotus goiavier) in three cities (Kuala Lumpur, Malaysia; Jakarta, Indonesia and Metro Manila, Philippines). The approach identifies potential priority corridors for ecological connectivity networks. The study combined circuit models, connectivity analysis and least-cost models to identify potential corridors by integrating structure and function of green space patches to provide reliable ecological connectivity network models in the cities. Relevant parameters such as landscape resistance and green space structure (vegetation density, patch size and patch distance) were derived from an expert and literature-based approach based on the preference of bird behaviour. The integrated models allowed the assessment of connectivity for both species using different measures of green space structure revealing the potential corridors and least-cost pathways for both bird species at the patch sites. The implementation of improvements to the identified corridors could increase the connectivity of green space. This study provides examples of how combining models can contribute to the improvement of ecological networks in rapidly expanding cities and demonstrates the usefulness of such models for biodiversity conservation and urban planning.Item Open Access Small Water Bodies in Great Britain and Ireland: Ecosystem function, human-generated degradation, and options for restorative action(Elsevier, 2018-07-26) Riley, William D.; Potter, Edward C. E.; Biggs, Jeremy; Collins, Adrian L.; Jarvie, Helen P.; Jones, J. Iwan; Kelly-Quinn, Mary; Ormerod, Steve J.; Sear, David A.; Wilby, Robert L.; Broadmeadow, Samantha; Brown, Colin D.; Chanin, Paul; Copp, Gordon H.; Cowx, Ian G.; Grogan, Adam; Hornby, Duncan D.; Huggett, Duncan; Kelly, Martyn G.; Naura, Marc; Newman, Jonathan R.; Siriwardena, Gavin M.Small, 1st and 2nd-order, headwater streams and ponds play essential roles in providing natural flood control, trapping sediments and contaminants, retaining nutrients, and maintaining biological diversity, which extend into downstream reaches, lakes and estuaries. However, the large geographic extent and high connectivity of these small water bodies with the surrounding terrestrial ecosystem makes them particularly vulnerable to growing land-use pressures and environmental change. The greatest pressure on the physical processes in these waters has been their extension and modification for agricultural and forestry drainage, resulting in highly modified discharge and temperature regimes that have implications for flood and drought control further downstream. The extensive length of the small stream network exposes rivers to a wide range of inputs, including nutrients, pesticides, heavy metals, sediment and emerging contaminants. Small water bodies have also been affected by invasions of non-native species, which along with the physical and chemical pressures, have affected most groups of organisms with consequent implications for the wider biodiversity within the catchment. Reducing the impacts and restoring the natural ecosystem function of these water bodies requires a three-tiered approach based on: restoration of channel hydromorphological dynamics; restoration and management of the riparian zone; and management of activities in the wider catchment that have both point-source and diffuse impacts. Such activities are expensive and so emphasis must be placed on integrated programmes that provide multiple benefits. Practical options need to be promoted through legislative regulation, financial incentives, markets for resource services and voluntary codes and actions.Item Open Access Using GIS-linked Bayesian Belief Networks as a tool for modelling urban biodiversity(Elsevier, 2019-05-30) Grafius, Darren R.; Corstanje, Ronald; Warren, Philip H.; Evans, Karl L.; Norton, Briony A.; Siriwardena, Gavin M.; Pescott, Oliver L.; Plummer, Kate E.; Mears, Meghann; Zawadzka, Joanna; Richards, J. Paul; Harris, Jim A.The ability to predict spatial variation in biodiversity is a long-standing but elusive objective of landscape ecology. It depends on a detailed understanding of relationships between landscape and patch structure and taxonomic richness, and accurate spatial modelling. Complex heterogeneous environments such as cities pose particular challenges, as well as heightened relevance, given the increasing rate of urbanisation globally. Here we use a GIS-linked Bayesian Belief Network approach to test whether landscape and patch structural characteristics (including vegetation height, green-space patch size and their connectivity) drive measured taxonomic richness of numerous invertebrate, plant, and avian groups. We find that modelled richness is typically higher in larger and better-connected green-spaces with taller vegetation, indicative of more complex vegetation structure and consistent with the principle of ‘bigger, better, and more joined up’. Assessing the relative importance of these variables indicates that vegetation height is the most influential in determining richness for a majority of taxa. There is variation, however, between taxonomic groups in the relationships between richness and landscape structural characteristics, and the sensitivity of these relationships to particular predictors. Consequently, despite some broad commonalities, there will be trade-offs between different taxonomic groups when designing urban landscapes to maximise biodiversity. This research demonstrates the feasibility of using a GIS-coupled Bayesian Belief Network approach to model biodiversity at fine spatial scales in complex landscapes where current data and appropriate modelling approaches are lacking, and our findings have important implications for ecologists, conservationists and planners.Item Open Access What do we need to know to enhance the environmental sustainability of agricultural production? A prioritisation of knowledge needs for the UK food system(MDPI, 2013-07-17T00:00:00Z) Dicks, Lynn V.; Bardgett, Richard D.; Bell, Jenny; Benton, Tim G.; Booth, Angela; Bouwman, Jan; Brown, Chris; Bruce, Ann; Burgess, Paul J.; Butler, Simon J.; Crute, Ian; Dixon, Frances; Drummond, Caroline; Freckleton, Robert P.; Gill, Maggie; Graham, Andrea; Hails, Rosie S.; Hallett, James; Hart, Beth; Hillier, Jon G.; Holland, John M.; Huxley, Jonathan N.; Ingram, John S. I.; King, Vanessa; MacMillan, Tom; McGonigle, Daniel F.; McQuaid, Carmel; Nevard, Tim; Norman, Steve; Norris, Ken; Pazderka, Catherine; Poonaji, Inder; Quinn, Claire Helen; Ramsden, S. J.; Sinclair, Duncan; Siriwardena, Gavin M.; Vickery, Juliet A.; Whitmore, A. P.; Wolmer, William; Sutherland, William J.Abstract: Increasing concerns about global environmental change and food security have focused attention on the need for environmentally sustainable agriculture. This is agriculture that makes efficient use of natural resources and does not degrade the environmental systems that underpin it, or deplete natural capital stocks. We convened a group of 29 ‘practitioners' and 17 environmental scientists with direct involvement or expertise in the environmental sustainability of agriculture. The practitioners included representatives from UK industry, non-government organizations and government agencies. We collaboratively developed a long list of 264 knowledge needs to help enhance the environmental sustainability of agriculture within the UK or for the UK market. We refined and selected the most important knowledge needs through a three-stage process of voting, discussion and scoring. Scientists and practitioners identified similar priorities. We present the 26 highest priority knowledge needs. Many of them demand integration of knowledge from different disciplines to inform policy and practice. The top five are about sustainability of livestock feed, trade-offs between ecosystem services at farm or landscape scale, phosphorus recycling and metrics to measure sustainability. The outcomes will be used to guide ongoing knowledge exchange work, future science policy and funding.