A 2017 study by Lancet Planet Health found that by 2071, heatwaves could lead to the death of 350 Maltese people each year. In fact, researchers are estimating that 99% of future weather-related deaths will be due to heatwaves. The impacts of heatwaves are being compounded by the increased urbanisation of Malta, which is leading to the formation of an Urban Heat Island (UHI), a phenomenon where simultaneously, one will find urban areas recording considerably higher temperatures than rural areas. UHIs result in uncomfortably hot air temperatures, especially in summer, and with global warming predicting hotter temperatures for Malta and more intense heatwaves, UHIs may turn into a deadly reality for the most vulnerable, including infants, the sick and the elderly.
To understand UHIs, take a look at this map of New York City taken by NASA.
Dark green areas on the map to the left show areas that have dense vegetation. Now look to the map on the right and notice how the same dark green regions coincide with cooler regions marked in dark purple.
The same is happening in Malta right now. The urbanisation of the Maltese islands without adequate planning is having drastic impacts on the standard of living in our localities, with some parts being overpopulated. For example, the population density in the harbour area is 3297.25 people per square kilometre – almost two and a half times the national population density. More worryingly though is that, already in 2013, Eurostat data showed that almost a third (32.9%) of the Maltese land territory is covered in artificial surface, with 19% of this artificial surface being in built up areas. These figures make Malta the country with the highest developed land area in the EU, which on average, only has 4.7% artificial cover.
A UHI is therefore occurring because moist vegetative cover has been replaced with city-construction materials such as asphalt and concrete, which do not reflect, but rather absorb much of the sun’s heat. For example, road surfaces can sometimes reach a temperature of 50˚C higher than the surrounding temperature. Cities with narrow streets, surrounded by high buildings and few open spaces, compound the problem by limiting the cooling effect of wind movements. Construction material also increases indoor temperatures, creating higher demand for air conditioning, which not only results in higher electricity bills, but also leads to frequent summer power cuts, and the dumping of heat into the already hot outdoors. Finally, car exhausts also increase city temperatures, which is higher when drivers leave their air-conditioning switched on to counter the heat outside.
On the other hand, vegetation is not prone to this heating effect. When plants absorb the sun’s heat, they create a process of evaporation and transpiration, which converts stored liquid water into vapour, cooling the surrounding area. Furthermore, trees provide shade, which prevents solar energy from reaching other surfaces, not to mention the embellishing effect and clean city air.
A 2016 study by Jonathan Scicluna reported on the Maltese localities suffering most from the effects of UHIs, with the high-density residential peripheries of Birkirkara being the hottest part of the island (temperature 8% hotter than average) and the countryside parts of Siġġiewi being the coolest (temperature 6.3% cooler than average).
Source: Scicluna, 2016
Data shows that UHI intensifies on entering an urban region. However, it also appears to depend on the size of the town or village. It is obvious therefore that city planning through the construction material used, water management, and green and open spaces are all factors that can lessen UHI and possibly save lives. One would be surprised by the numerous options available to stop the vicious downward spiral of UHI.
Paved surfaces represent most of the surface area of a city, which are one of the main factors for higher city temperatures. Using ultra-thin white topping (UTW) for road surfaces and car parks improves solar heat reflectivity. New technologies also allow for permeable asphalt and pavements, which would act similarly to natural soil by absorbing rainwater run-off and providing the associated cooling benefits of water evaporation.
Light-coloured roof tops (cool roofs) are also quick wins in terms of combatting UHI. In fact, the US Department of Energy Oak Ridge National Laboratory introduced an energy savings calculator for its citizens so that they can estimate the energy savings associated with cool roof technologies.
Increased vegetation in urban areas can also cool city temperatures thanks to the natural processes of soil evaporation and plant transpiration. Singapore has for some time now been carrying forward an urban forest project, which is turning a concrete jungle into a cool, green paradise. The benefits of urban forests are not limited to aesthetics and cooling, but also include energy savings, reduced carbon dioxide emissions, air quality improvements, reduced rainwater runoff and increased property value.
Imagine if we could turn our concrete cities to urban forests such as this. Source: ArchitectureAU
An extension to urban forests are green roofs, which combine the benefits of urban forests and cool roofs. Green roofs can be installed in private residences and large industrial facilities alike. In fact, Scicluna also suggested that green roofs may be the most feasible solution in reducing UHIs in Malta.
Vivacity, a local company, makes green roofs such as this, possible
Whether we admit it or not, humans are as much a part of the same intrinsic ecosystem that surrounds them as the smallest species of plant in their environment. Malta has no choice but to adapt quickly to withstand longer and warmer periods and more frequent heat waves.
Forzieri, G., Cescatti, A., Batista, F. & Silva, L. F., 2017. Increasing risk over time of weather-related hazards to the European population: a data-driven prognostic study. Lancet Planet Health.
Hulley, M., 2012. The urban heat island effect: causes and potential solutions.
Malta Independent, 2017. Heat waves forecast to kill 350 Maltese a year by 2071. [Online] Available at: http://www.independent.com.mt/articles/2017-08-06/local-news/Heat-waves-forecast-to-kill-350-Maltese-a-year-by-2071-6736177474 [Accessed 2021].
NASA, n.d. Can you explain the urban heat island effect?. [Online] Available at: https://climate.nasa.gov/faq/44/can-you-explain-the-urban-heat-island-effect/ [Accessed 2021].
Scicluna, J., 2016. The Urban Heat Island effect in Malta and the adequacy of green roofs in its mitigation.