Urban development, land sharing and land sparing: the importance of considering restoration

Abstract

1. At present, there is limited knowledge of how best to reconcile urban development with biodiversity conservation, and in particular whether populations of wild species would be greater under low-density housing (with larger gardens), or high-density housing (allowing more area to be left as undeveloped green spaces). The land sharing/sparing frameworkoriginally developed in the context of farmingcan be applied to address this question. 2. We sampled the abundance of trees in the city of Cambridge, UK, along a gradient of human density. We designed different scenarios of urban growth to accommodate the human population predicted in 2031. For each scenario, we projected the future city-wide tree population size and quantified its carbon sequestration potential. We also considered, for the first time in an urban sharing-sparing context, the implications of habitat restoration on degraded urban green space. 3. We found that the density of most native and non-native tree species is presently highest in areas of low human density, compared to both higher density areas and green space (which is largely maintained with few trees). However, restoring woodland in green spaces would lead to far greater densities of native trees than on any existing land use. Hence, provided >2% of green space is restored, native tree population sizes would be larger if urban growth followed a land-sparing approach. Likewise, carbon sequestration would be maximised under land sparing coupled with restoration, but even so only a maximum of 2Á5% of the city's annual greenhouse gas emissions could be offset. 4. Although both tree populations and carbon storage thus appear to benefit from land-sparing development, the risk that this might widen the existing disconnect between people and nature must also be addressedperhaps through a combination of adding housing in lowdensity areas while ensuring these are in close proximity to high-quality green space. 5. Synthesis and applications. In regions which have already been cleared of intact habitat, a combination of land-sparing urban development with the restoration of green space could accommodate urban population growth whilst dramatically improving the existing status of local tree populations. Where cities are expanding into intact habitat, the merits of urban development by land sparing may be even more pronounced. Studies in such regions are urgently needed.

Land‐sharing vs. land‐sparing urban development modulate predator–prey interactions in Europe

“…Earlier studies have suggested that land‐sparing development will benefit urban biodiversity over land‐sharing development among different taxa, including plants (Collas et al. ), arthropods (Soga et al. ), mammals (Caryl et al.…”

Compact cities or sprawling suburbs? Optimising the distribution of people in cities to maximise species diversity

“…Similarly, Stott et al. () emphasised the importance of land sparing for ecosystem services, and Collas, Green, Ross, Wastell, and Balmford () highlighted that land sparing combined with restoration would most benefit tree species conservation in Cambridge, United Kingdom. Although each of these studies support land sparing, it is important to note that this does not mean that “spared” landscapes are free of humans, but merely that they are free of urban infrastructure.…”

“…Many actions can be taken to enhance urban environments for nature conservation, including increasing their value for native bird species. Restoration of native vegetation in existing green and open spaces, such as along urban streams and in parklands, provides an opportunity to increase the extent of habitats (Collas et al., ). Given an ongoing increase in urban populations and expansion of urban boundaries, strategic zoning and protection of existing native vegetation on the fringes of urban environments combined with policies that encourage urban infilling—particularly within industrial and residential land—will be critical for future conservation.…”

“…Caryl et al (2015)also working within the Greater Melbourne region-showed that land sparing would be preferable to land sharing for most species of insectivorous bats, and Villaseñor, Tulloch, Driscoll, Gibbons and Lindenmayer (2017) showed the benefits of compact development for ground-dwelling and arboreal mammals in south-eastern New South Wales, Australia. Similarly, Stott et al (2015) emphasised the importance of land sparing for ecosystem services, and Collas, Green, Ross, Wastell, and Balmford (2017) highlighted that land sparing combined with restoration would most benefit tree species conservation in Cambridge, United Kingdom. Although each of these studies support land sparing, it is important to note that this does not mean that "spared" landscapes are free of humans, but merely that they are free of urban infrastructure.…”

What Have We Learned from the Land Sparing-sharing Model?

“…The original formulation of the land sparing-sharing framework omits some complexities, but it can be and already has been modified to incorporate many of these, including spatial configuration and the influence of edge effects [60,61]; the influence of changing diets and reducing food waste [50]; inclusion of some ecosystem services [4,7,50,62]; prediction of the effects of specific public policies [63]; and application to forestry [64,65], urban planning [66][67][68][69] and marine conservation [70]. It is a model, and so all assumptions can be varied and tested.…”