Urban biodiversity conservation:Sharing the human habitat
Yusef Samari
Outline
• Urbanisation trends• Characteristics of the urban habitat• Why conserve urban biodiversity?• Managing urban green spaces for biodiversity: quantifying potential trade-offs
All organisms change their environment
• Ecosystem engineers• “It may be doubted whether there are many other animals which have played so important a part in the history of the world, as have these lowly organized creatures.” - Charles Darwin 1881
Yiwu, east China
Competition for the earthworm?
Humans are becoming an urban species
• 30% urban in 1950 – 66% urban 2050United Nations, Department of Economic and Social Affairs, Population Division (2014).World Urbanization Prospects: The 2014 Revision, Highlights (ST/ESA/SER.A/352).
What is urban?
• Scotland – settlement of 3,000+• England/ Wales– settlement of 10,000+• Finland – settlement of 200, no more than 50m between buildings
• India – settlement of 5000, min density of 400/ km2, >75% “main male working population not employed in agriculture”
• Increase in population density• Increase in concentration of built structures
Extent of the urban habitat
Due to increase by 1.2 million km2 by 2030 – 300% compared to 2000Seto, K. C., Güneralp, B., & Hutyra, L. R. (2012). Global forecasts of urban expansion to 2030 and direct impacts on biodiversity and carbon pools. Proceedings of the National Academy of Sciences, 109(40): 16083-16088.
Characteristics of the urban habitat
• Converting land• Changing climate
• Moving species around
The Anthropocene epoch
Steffen, W., Broadgate, W., Deutsch, L., Gaffney, O., & Ludwig, C. (2015). The trajectory of the Anthropocene: the great acceleration. The Anthropocene Review 2(1): 81-98.
Cities are habitat mosaics Urban Savanna
• High habitat heterogeneity (scale dependent)
• Fragmented vegetation
A global city environment?
Groffman, P. M., Cavender-Bares, J., Bettez, N. D., Grove, J. M., Hall, S. J., Heffernan, J. B., ... & Nelson, K. (2014). Ecological homogenization of urban USA. Frontiers in Ecology and the Environment 12(1): 74-81.
Socioeconomics / culture as ecological drivers
Hope, D., Gries, C., Zhu, W., Fagan, W. F., Redman, C. L., Grimm, N. B., ... & Kinzig, A. (2003). Socioeconomics drive urban plant diversity. Proceedings of the National Academy of Sciences 100(15): 8788-8792.
Why conserve urban biodiversity?
Threats: homogenisation
• Urban environments are more similar to each other than their rural counterparts
• Humans may have similar preferences around the world
• May filter a suite of closely related species, from the regional pool – Generalists that are well adapted to the urban environment
– Plant species that people like
Threats: homogenisation
Groffman, P. M., Cavender-Bares, J., Bettez, N. D., Grove, J. M., Hall, S. J., Heffernan, J. B., ... & Nelson, K. (2014). Ecological homogenization of urban USA. Frontiers in Ecology and the Environment 12(1): 74-81.
Threats: extinctions
Aronson, M. F., La Sorte, F. A., Nilon, C. H., Katti, M., Goddard, M. A., Lepczyk, C. A., ... & Dobbs, C. (2014, April). A global analysis of the impacts of urbanization on bird and plant diversity reveals key anthropogenic drivers. Proc. R. Soc. B 281 (1780) 20133330
Jennifer Owen’s garden
A suburban garden in Leicester with 2,673 species of flora and fauna, including474 different plants, 80 spiders, 183 bugs,375 moths442 beetles.
Cities are not biodiversity deserts
Cities are not biodiversity deserts
Sirohi, M. H., Jackson, J., Edwards, M., & Ollerton, J. (2015). Diversity and abundance of solitary and primitively eusocial bees in an urban centre: a case study from Northampton (England). Journal of Insect Conservation, 19(3), 487-500.
Cities are hotspots for threatened species
• Challenge: Most areas of forecasted future urban expansion are in “biodiversity hotspots” – high biodiversity threat through habitat loss
• Opportunity: We can protect a relatively large number of species through a relatively small land area (with appropriate management)
Ives, C. D., Lentini, P. E., Threlfall, C. G., Ikin, K., Shanahan, D. F., Garrard, G. E., ... & Rowe, R. (2016). Cities are hotspots for threatened species. Global Ecology and Biogeography, 25(1), 117-126.
Human benefits of urban biodiversity
Fuller, R. A., Irvine, K. N., Devine-Wright, P., Warren, P. H., & Gaston, K. J. (2007). Psychological benefits of greenspace increase with biodiversity. Biology Letters 3(4): 390-394.
How to conserve urban biodiversity?
• Grow cities in ways that minimise their impact on existing biodiversity
• Improve habitat in cities to support more biodiversity
Enhancing biodiversity in urban green spaces
Why green spaces?
• Urban green spaces such as parks, roadside verges and golf courses typically cover a large proportion of urban area
• Recent research has shown they support low pollinator populations per unit area
• Good target for improvement
• City councils manage large areas on limited budgets
• Floral meadows are expensive
Constraints: cost
Urban green spaces are highly managed ecosystems
• Mowed 2-6 times per month for 9 months• Herbicide, fertiliser, etc.
Biodiversity could be improved by managing more
…or managing less
What is the relationship between investment and biodiversity value per
unit area?
Constraints: public appreciation
• Biodiversity is (often) messy
• Features that people don’t like, don’t tend to stick around
What is the relationship between biodiversity value and public
appreciation?
Does biodiversity influence human behaviour?
What are the trade-offs between management cost, biodiversity value
and amenity value?
Edinburgh as a testing ground
• ~60 floral meadows throughout the city– High investment
• “Naturalised Grassland” created by relaxing mowing regime– Low investment
Questions
• How do the management cost and biodiversity value of the different management options vary with area?
• Do the different options vary in the biodiversiy they support?
• Which of the different management options is preferred by humans?
• How do the different management options influence human behaviour (litter, dog fouling)?
Measurements
• 20-30 sites, each with annual meadow, naturalised grassland and amenity grassland (control) areas
• Survey for plants, pollinators, ground-dwelling invertebrates, birds
• Measure human behaviour (litter, dog fouling, time spent in area)
• Measure human perception
ExpectationsNaturalised grassland Floral meadow
Outcomes
• Platform for future experiments• A model to inform city councils how to best manage an urban green space for biodiversity and people, on a given budget