Ranking of invasive spread through urban green areas in the world’s 100 most populous cities

Urban landscapes are highly fragmented (leading to the extinction of native species) as well as transformed and disturbed (creating novel environments). Such conditions provide non-native species with opportunities to establish and spread through “urban green areas” (UGAs). UGAs can serve as stepping stones for many alien species to recruit and may become sources of propagules to launch invasions in adjoining natural ecosystems. There is great diversity in the spatial structures of UGAs worldwide; these are determined by the city’s level of development, human density, urban planning policy, and history. We explore the invasion risks of, and the potential of invasive spread in, UGAs in the world’s 100 most populous cities (in 40 countries). Based on maps of enhanced vegetation index at 250 m resolution over the extent of 25 by 25 km for each city centre, we simulate the invasion and spread of a reference species (a virtual ruderal invasive species) from the city centre into surrounding urban or rural areas. Doing so allowed us to provide an objective baseline for comparing urban susceptibility to such invasions across diverse cultures, histories and societies. We derive the global ranking of invasive spread potential for each city based on the rate of spread of the reference species, and the ranking of 40 countries, based on the average rate of spread in their cities. We explore correlates of spread rates after 100 time steps (years) by examining the roles of climate (mean annual temperature and rainfall), human demography (city population size and growth rate), and socio-economic indicators [human footprint, human development index and gross domestic product (GDP) per capita]. Small city population size and high GDP per capita are the only significant predictors of high potential for invasive spread. Among the G20 countries, Canada, South Korea, South Africa, France, USA and Brazil all feature in the top-10 countries, and Atlanta, Washington, D.C. and Dallas in the USA, Chittagong in Bangladesh, Toronto in Canada and Brasilia in Brazil are listed among the top 10 cities overall. Our results can serve as a global baseline assessment of invasive spread risks through UGAs, and call for improved protocols for monitoring, planning and management of UGAs.

[1]  I. Kowarik,et al.  Long‐Distance Dispersal of Plants by Vehicles as a Driver of Plant Invasions , 2007, Conservation biology : the journal of the Society for Conservation Biology.

[2]  Susan I. Stewart,et al.  Housing is positively associated with invasive exotic plant species richness in New England, USA. , 2010, Ecological applications : a publication of the Ecological Society of America.

[3]  N. S. Williams,et al.  Patterns of exotic plant invasions in fragmented urban and rural grasslands across continents , 2008, Landscape Ecology.

[4]  B. Maxwell,et al.  Cross-scale management strategies for optimal control of trees invading from source plantations , 2014, Biological Invasions.

[5]  F. Rozé,et al.  The effects of urban or rural landscape context and distance from the edge on native woodland plant communities , 2010, Biodiversity and Conservation.

[6]  Alan Hastings,et al.  Autocorrelated environmental variation and the establishment of invasive species , 2016 .

[7]  M. McKinney,et al.  Effects of urbanization on species richness: A review of plants and animals , 2008, Urban Ecosystems.

[8]  D. Richardson,et al.  Modelling Spread in Invasion Ecology: A Synthesis , 2010 .

[9]  D. Richardson,et al.  The roles of habitat features, disturbance, and distance from putative source populations in structuring alien plant invasions at the urban/wildland interface on the Cape Peninsula, South Africa. , 2006 .

[10]  Executive Summary.  World Urbanization Prospects: The 2018 Revision , 2019 .

[11]  Richard A. Wadsworth,et al.  Simulating the spread and management of alien riparian weeds: are they out of control? , 2000 .

[12]  Anna K. Gdula,et al.  “The rich get richer” concept in riparian woody species – A case study of the Warta River Valley (Poznań, Poland) , 2015 .

[13]  Philip E. Hulme,et al.  Herbarium records identify the role of long‐distance spread in the spatial distribution of alien plants in New Zealand , 2010 .

[14]  S. Weiss,et al.  Cars, Cows, and Checkerspot Butterflies: Nitrogen Deposition and Management of Nutrient‐Poor Grasslands for a Threatened Species , 1999 .

[15]  R. Scheibling,et al.  Range expansion by invasive marine algae: rates and patterns of spread at a regional scale , 2009 .

[16]  O. Phillips,et al.  Extinction risk from climate change , 2004, Nature.

[17]  Richard N. Mack,et al.  Controlling the spread of plant invasions: The importance of nascent foci. , 1988 .

[18]  Jan Pergl,et al.  Low persistence of a monocarpic invasive plant in historical sites biases our perception of its actual distribution , 2012, Journal of biogeography.

[19]  Wilfried Thuiller,et al.  From introduction to equilibrium: reconstructing the invasive pathways of the Argentine ant in a Mediterranean region , 2009 .

[20]  U. Cascorbi.  Integration of invasion ecology theories into the analysis of designed plant communities: a case study in Southern Germany , 2007, Landscape Ecology.

[21]  J. Pino,et al.  Examining the role of landscape structure and dynamics in alien plant invasion from urban Mediterranean coastal habitats , 2015 .

[22]  James E. Wilen,et al.  Optimal spatial control of biological invasions , 2012 .

[23]  Ross A. Bradstock,et al.  Countervailing effects of urbanization and vegetation extent on fire frequency on the Wildland urban interface: disentangling fuel and ignition effects , 2014 .

[24]  R. Congalton,et al.  Incipient Invasion of Urban and Forest Habitats in New Hampshire, USA, by the Nonnative Tree, Kalopanax septemlobus , 2015, Invasive Plant Science and Management.

[25]  Byungseol Byun,et al.  The pattern of landscape patches and invasion of naturalized plants in developed areas of urban Seoul , 2005 .

[26]  D. Richardson,et al.  Invasion trajectory of alien trees: the role of introduction pathway and planting history , 2014, Global change biology.

[27]  Andrew Gonzalez,et al.  The inflationary effects of environmental fluctuations in source–sink systems , 2002, Proceedings of the National Academy of Sciences of the United States of America.

[28]  Christos T. Nakas,et al.  Life history evolution in a globally invading tephritid: patterns of survival and reproduction in medflies from six world regions , 2009 .

[29]  M. Leishman,et al.  Post‐fire vegetation dynamics in nutrient‐enriched and non‐enriched sclerophyll woodland , 2005 .

[30]  C. Hui,et al.  Integrating age structured and landscape resistance models to disentangle invasion dynamics of a pond-breeding anuran , 2017 .

[31]  Lisa J. Rew,et al.  The Rationale for Monitoring Invasive Plant Populations as a Crucial Step for Management , 2009, Invasive Plant Science and Management.

[32]  Stephen P Ellner,et al.  Cryptic Population Dynamics: Rapid Evolution Masks Trophic Interactions , 2007, PLoS biology.

[33]  J. Gamarra,et al.  Metapopulation Ecology , 2007 .

[34]  Lina Straigyte,et al.  Comparison of neophyte communities of Robinia pseudoacacia L. and Acer negundo L. in the eastern Baltic Sea region cities of Riga and Kaunas , 2015 .

[35]  Brian Huntley,et al.  Impacts of landscape structure on butterfly range expansion , 2001 .

[36]  T. Geisel,et al.  The scaling laws of human travel , 2006, Nature.

[37]  J. L. Parra,et al.  Very high resolution interpolated climate surfaces for global land areas , 2005 .

[38]  Philip E. Hulme,et al.  Biological invasions: winning the science battles but losing the conservation war? , 2003, Oryx.

[39]  D. Richardson,et al.  A river runs through it: Land-use and the composition of vegetation along a riparian corridor in the Cape Floristic Region, South Africa , 2010 .

[40]  K. Prach,et al.  INVASIONS OF ALIEN PLANTS INTO HABITATS OF CENTRAL EUROPEAN LANDSCAPE : AN HISTORICAL PATTERN , 2007 .

[41]  Niklaus E. Zimmermann,et al.  Neophyte species richness at the landscape scale under urban sprawl and climate warming , 2009 .

[42]  R. Levins,et al.  The effect of random variations of different types on population growth. , 1969, Proceedings of the National Academy of Sciences of the United States of America.

[43]  C. Edwards.  Managing and Controlling Invasive Rhododendron , 2006 .

[44]  H. Dingle,et al.  The biology of post-invasion events , 1996 .

[45]  C. M. Harris,et al.  Invasive species control: Incorporating demographic data and seed dispersal into a management model for Rhododendron ponticum , 2009, Ecol. Informatics.

[46]  K. Evans,et al.  Flexible dispersal strategies in native and non-native ranges: environmental quality and the 'good-stay, bad-disperse' rule , 2012 .

[47]  S. Levin,et al.  Long‐Distance Dispersal1 , 2003 .

[48]  Philip E. Hulme,et al.  Spatio-temporal dynamics of plant invasions: Linking pattern to process , 2005 .

[49]  John A. Silander,et al.  Invasion Dynamics , 2017 .

[50]  David M. Richardson,et al.  Small urban centres as launching sites for plant invasions in natural areas: insights from South Africa , 2017, Biological Invasions.

[51]  Steven I. Higgins,et al.  USING A DYNAMIC LANDSCAPE MODEL FOR PLANNING THE MANAGEMENT OF ALIEN PLANT INVASIONS , 2000 .

[52]  Brett A. Melbourne,et al.  Highly Variable Spread Rates in Replicated Biological Invasions: Fundamental Limits to Predictability , 2009, Science.