Planting for a cooler city

The use of vegetation in the city can provide an effective way to mitigate heat as plants can help to provide shade, reflect heat and provide cooling through evapotranspiration¹ . Vegetation can be incorporated the built environment through street trees, parks and plazas, while vegetation can also be incorporated as building elements through balcony plantings, living walls and green roofs. For the Darwin CBD, research showed that shading from vegetation reduced street and pavement surface temperatures by 10‒23°C2.

Landscaping that increases vegetation in the city not only helps to cool buildings and its environment but also can help improve local air quality and creates inviting spaces for residents to engage with nature and help visually soften the urban environment.

Opportunities in Darwin

Significant landscape enhancements have and are being undertaken in the public domain of the Darwin CBD, yet landscaping in the private domain also plays a significant role in establishing and improving the city’s amenity.
Darwin’s tropical climate lends itself well to dense plantings at an impressive scale. However, many of the trees perceived as being part of Darwin’s character are exotic imports and often require additional watering through the long dry season to maintain their health.

The widespread damage caused by Tropical Cyclone Marcus in 2018 with the loss of thousands of trees in Darwin’s public spaces³ highlights the need to consider the cyclone resilience of different tree species, and how the impact of extreme wind events on trees can be mitigated through practices such as less frequent irrigation that can encourages deeper root growth⁴. While a changing climate will likely impact on the suitability of different vegetation species to thrive in the future⁵.

So how can the tropical ‘dream’ be sustainably aligned with the practical realities of Darwin’s wet/dry tropics? The answers may lie in taking cues from nature. For example – while palm trees may not naturally be as prevalent as they have been commonly planted in the CBD, they are often found in gorges and near water bodies where taller trees have created a protective upper canopy.

Key points to consider

• Balcony planting that provide amenity and shading benefits to residents, while also considering benefits to adjacent public domain
• Selection of plants that can be resilient to the dry season and a changing climate
• Plant selections to be guided by different contexts across the city to maximize their value in providing community benefits such as shading
• Watering regimes and drainage that encourage the development of deep root systems