Can urban landscape design save our cities from scorching heat waves?

In 2020, the world experienced the hottest September on record. Fast-forward to 2023, and this scorching reality intensified, with NASA ranking 2022 as the fifth warmest year, with the hottest September in 174 years. The intensity of heat is on the rise, and the occasional yet severe heat waves have devastating effects. A ‘heat wave’ is a period when temperatures are unusually high, defined by the World Meteorological Organisation as the period when daily maximum temperatures exceed the average maximum temperature by 5 degrees Celsius.

Urban areas experience heat waves more intensely than their rural counterparts, ranging from a 3–6-degree differential, according to studies conducted in major metropolitan areas. Urban design, or its absence, significantly contributes to this heat challenge. Extensive stretches of exposed asphalt, common in car-centric urban layouts, along with concrete-clad buildings and sidewalks, absorb heat throughout the day and release it at night. Glass facades increase the greenhouse effect, trapping heat within buildings. This is exacerbated by a lack of cross-ventilation and the widespread use of inefficient localised cooling devices, like air conditioners, which not only consume significant energy but also release excess heat.

Climate change, a cyclical process predating human existence, occurred over millions of years. A 2010 NASA study reveals that throughout the last two million years, global warming has occurred on multiple occasions, typically taking around 5,000 years for the planet to warm by 5 degrees C. However, the striking statistic is that in the past century alone, the temperature has risen by 0.7 degrees Celsius, a rate approximately 10 times faster than the average pace of warming during ice-age recovery. Projections for the
next century predict a rate of warming
that is at least 20 times faster than the historical norm.

Post-industrialization, the human footprint has expanded rapidly, significantly contributing to systemic land changes and severely altering the environment in some parts of the world. It is time we acknowledge the interconnectedness of human activities with the environment and have this harmony reflected in urban development.
Traditionally, cultures were anchored around fostering a lifestyle harmonious with nature’s rhythms, with minimally invasive everyday rituals. Rooted innately in the natural world, they embraced an understanding of actions and their future consequences. Instead of fighting the changes in the climate, like our forefathers, we can learn to design our cities in harmony with nature’s rhythms and build around them.

Historically, adaptations to varying climates had a deep-rooted understanding of the materials shaping the construction of settlements. Recognising that certain building materials absorb, radiate, or transform heat allowed vernacular practices to tailor building construction to regional climates. However, contemporary urban cores often adopt a one-size-fits-all approach, employing materials like glass, concrete, and asphalt regardless of contextual relevance. Yet, worldwide, there are compelling examples of innovative adaptations to extreme climatic conditions. The 2013 Ahmedabad Heat Action Plan introduced a cool roof initiative for informal settlements, lowering indoor temperatures by painting roofs white, a colour that reflects 60% more heat than grey.

Green corridors, another impactful strategy, have demonstrated to their efficacy in mitigating rising temperatures. Examples include the Manhattan Waterfront Greenway Corridor, the interconnected network of greenery called ‘Corredores Verdes’ in Medellin, and the Cheonggyecheon in Seoul.

These ecological corridors not only lower temperatures but also serve as essential sinks for capturing carbon dioxide and producing pure atmospheric oxygen. They facilitate groundwater infiltration, benefiting local watersheds and contributing to the overall water cycle. Besides, they also have the potential to remediate pollutants that have leached into the soil. Dense networks of trees are highly adept at efficiently treating the heat energy that we are unable to cope with, helping us combat the devastating effects of an industrially overengineered world.

Embracing nature as an ally presents a collective opportunity to make a significant impact. By introducing incentives for planting more trees, we have the potential to substantially enhance the tree canopy in urban areas. Individuals, communities, landscape architects, urban designers, and policymakers can all play pivotal roles in advocating for the planting of native trees, creating green corridors, and enriching the local flora and fauna.

On a personal level, individuals can gift trees for holidays or plant them as memorials, adding enduring value and vibrant colours to their homes and neighbourhoods. Schools can instill environmental consciousness in children by encouraging tree planting and care, fostering a connection with nature for a better environment.

On a larger scale, landscape architects and urban designers can integrate pre- and post-design solar analysis into their projects, ensuring they understand the impact of the design and the incorporation of diverse native trees in it.

Policymakers can contribute by offering tax incentives to residents with large shade trees. Certain countries incentivize alternative climate adaptation methods, like green roofs and vertical gardens, and some jurisdictions strictly regulate tree removal, requiring mitigation and replacement to maintain or increase tree canopy coverage. When this approach is scaled and replicated across entire
communities, it results in lower temperatures, reduced energy costs, and the establishment of shaded zones for people to find respite.

Nature and its intricate systems are ephemeral and possess the inherent ability to regenerate and heal. Therefore, it becomes our duty to glean insights from these natural processes and formulate environments and policies that promote the creation of breathable and resilient spaces, allowing us to thrive in sync with nature even in dense urban areas. By utilising the diverse array of resources bestowed upon us by nature, we can design environments that align with the earth’s innate resilience. Saving our planet is not solely the responsibility of others; it is a shared obligation that extends to everyone who calls the Earth home, ensuring a sustainable legacy for ourselves and future generations.

(The writer is a landscape architect and a principal at a Florida-based design studio)