Land-use history causes differences in park nighttime cooling capacity and forest structure

Abstract

Cities are temporally dynamic ecosystems that experience continuous redevelopment over time. Urban parks, which provide critical benefits to resident wellbeing, are developed on different land-use types and contain natural elements that are susceptible to the effects of historical decision making. Thus, understanding the current day functioning of our citys ecosystems and planning for the equitable distribution of park benefits in the future requires incorporation and understanding of the impacts of historical decision-making. We measured neighbourhood socio-demographic composition, forest structure, and the cooling effect of 33 sites in parks across Montreal, each with a past land-use in one of three classes: agricultural, forested, or industrial. We asked: 1) what are the effects of historical land-use on current park forest structure, diversity, and consequently the capacity to provide cooling? 2) how do surrounding communities differ around parks of each historical land-use type, and what are the implications for equitable access to cooling? We found that forest structure and cooling capacity differed across past land-use type, and forest structure has complex relationships with park cooling capacity. Our results provide evidence of historical environmental injustice impacting current day cooling capacity for marginalized groups. Previously industrial parks had less cooling capacity at night, while simultaneously being surrounded by communities with higher proportions of immigrants, and lower median incomes than Montreals average. However, daytime cooling capacity was similar across past land-use type, highlighting the importance of current management decisions to provide a critical ecosystem service, temperature mitigation, regardless of a sites history. Planting areas of small, dense forest stands with trees >= 5 cm DBH within urban parks can help augment daytime cooling benefits in the city but may hinder nighttime cooling. To provide both nighttime and daytime cooling, a mixed management strategy of park trees is required, where small and large trees are incorporated at different densities. Finally, we find evidence of gentrification surrounding all park sites, emphasizing the complex socioecological dynamics of green infrastructure and the need for community-led greening projects paired with social housing policies.