Sustainable Disaster Risk Reduction & Climate Change Adaptation in Cities

Mart van der Marel talks us through his research into environmental risk reduction, and what climate change could mean for our cities.

Due to human activities, the earth’s climate is increasingly being nudged towards a state of warmer temperatures and more extreme weather events. According to the Met Office, for example, heat waves could occur every other year by the middle of this century. This is quite alarming considering the death toll of over 20,000 caused by the European-wide heat wave in 2003. Urban areas are especially vulnerable because they are characterised by a great concentration of people, assets and are often located in highly exposed areas such as river floodplains or along the coast. Considering all of this, it is paramount that cities lower the risk from climate hazards and adapt to a changing climate to prevent the worst.

Research indicates that ecosystem services delivered by greenspaces have the potential to contribute to urban Disaster Risk Reduction (DRR) – including adaptation to the effects of climate change – in an environmentally, economically and socially durable way. This concept is coined Ecosystem-based Adaptation (EbA) in scientific literature and involves creating and enhancing greenspaces to generate ecosystem services that benefit hazard mitigation; trees, for example, provide shade during hot summer days and evaporate water, lowering temperatures (See the following table for more detail). During storms, plants and permeable surfaces will absorb water, reducing surface flooding.

Different types of Urban Green Infrastructure (UGI), modes of cooling provided by these during summer, and optimal locations for these to maximise cooling benefits (taken from Norton et al. (2015)).

Besides this, urban greenspace provides a variety of other benefits, including noise insulation and enhanced health and well-being as can be seen in the following figure.

Potential ecosystem services provided by urban greenspaces (adapted from Connop et al. (2016)).

Nevertheless, research on the practical use of EbA in urban areas remains scarce, and this is especially the case with regards to its impact on local DRR.

Inspired by a local initiative aimed at greening the University College London campus in central London, I investigated the potential value of EbA for the UCL Bloomsbury campus. Based on a literature analysis I decided to develop a range of scenarios reflecting uncertainty with regards to how climate-related hazards might evolve in light of climate change, and the degree to which EbA might be adopted on the campus.

Utilizing environmental, social and economic data, I found that the main climate-related hazards affecting the campus are heat waves and winter storms; heat waves are characterised by temperatures exceeding the normal average for an extended period, and winter storms are characterised by heavy precipitation and gale-force winds. Both of these hazards are expected to worsen as a result of climate change: We will very likely see – and are already seeing – a rise in the number of warm days and more frequent and intense storms with heavier precipitation and stronger wind speeds.

Below 2 maps are given, showing the importance of these two hazards for the UCL campus.

Spatial distribution of the heat vulnerability index grouped into 10 vulnerability classes. Bloomsbury outlined in Yellow in central London (adapted from Wolf et al. (2014)).

Flood risk from surface water. UCL Bloomsbury campus buildings in yellow (adapted from the Environment Agency).

Combining this information about future climate trends with data about the campus and the local greening initiative introduced above, future scenarios were developed for the year 2040. From this scenario analysis exercise, it emerged that greening of the UCL Bloomsbury campus can have a positive impact on local DRR over the next decades. It was found that the benefits become more evident as the extent to which the campus is greened increases; more trees and more permeable surfaces result in lower temperatures during heat waves and less surface flooding during winter storms.

However, it was also found that despite this, the implementation of EbA cannot completely offset the expected increase in losses from climate-related hazards over the next two decades. This means that the degree to which climate change strengthens climate-hazards will result in additional losses from heat waves and winter storms that are greater than the possible reduction of hazard losses we can achieve by extensive urban greening!

This makes it very clear that it is necessary to implement EbA measures alongside other effective DRR measures and parallel to climate change mitigation measures as part of an integrated and sustainable response to climate change.

To conclude I would like to note that further efforts into understanding the concrete value of EbA are valuable as the benefits of this method are broad and far-reaching, and not limited to DRR only. Moreover, the impact of EbA is highly dependent on the geographical location, thus requiring localised research efforts rather than a one-fits-all approach.

About the Author: Mart van der Marel is a UCL graduate with an MSc in Risk, Disaster and Resilience. He is passionate about the environment and creating a fair and sustainable future. You can email him at mart.marel.17@ucl.ac.uk.