Dr Stefano Moncada (Institute for European Studies) and Dr Charles Galdies (Institute of Earth Systems), both members of the Climate Change Platform of the University of Malta, have joined forces to participate with an international group of experts in an intercomparison study on the role of ecosystems services in the sustainability of major cities in the world. Access to this manuscript can be found online.

For this work, Galdies and Moncada merged processed satellite remote sensing information, geographical information systems and socio-demographic data to look at how the current green spaces in Valletta and associated urban green infrastructure are influencing the quality of the environment and of the health of its residents.

Calculations were made on the basis of the fact that 1 hectar of mixed tree area can remove 15 tonnes of particulates per year from the air. From a social point of view, green spaces generate employment and boost tourism, which is an important economic benefit.

The upper and lower Barakka gardens attract many Maltese and tourists all year round. The presence of fauna such as birds and insects should also be accounted for the significant recreational value given by these important spaces. From a climate resilience point of view, a single large tree can transpire 450 litres of water per day, consuming in the process some 1000 MJ of heat energy to drive the evaporative process. The presence of more trees is therefore able to cool the air temperatures within Valletta, thus reducing the urban heat island effect that this city generates. This will be especially meaningful during heat waves episodes, of which frequency is expected to increase in the coming decades.

This study concludes that comprehensive evaluations of the ecosystem services in major global cities should be undertaken, so as to prioritise areas where actions are needed in the short, medium and long-term. By doing so, city councils can pay greater attention to the potential of urban ecosystem services for improving the resilience and quality of life in their cities. This can be implemented, for instance, by ensuring that any building/restoration projects are not pursued to the disadvantage of green areas, or by implementing building codes which seek to reduce the risks of urban heat islands (for instance, by including greenery on roofs or on facades).

Another important recommendation made by this study is that city councils should make more use of smart technologies in city development plans, to better monitor, model and assess the environmental consequences and risks related to the depletion of ecosystem services, an area also targeted by the recent EU green plan for making the EU's society and economy sustainable.