Large trees can help cool urban heat islands, expert says

The Stockholm Environment Institute’s senior expert Kaidi Tamm told ERR’s Ringvaade that the largest urban heat islands are large car parks around shopping centres and sports fields with rubber surfaces.

Measurements taken in Tallinn showed that asphalt outside the Estonia Theatre reached up to 60 degrees Celsius on an ordinary summer day when the air temperature was 23 degrees. Tamm said air temperature and surface temperature must be distinguished, as the heat island effect can occur even when the weather is not especially hot if surfaces absorb and radiate heat.

In Tammsaare Park, the surface temperature of a paved area in direct sunlight can reach around 40 degrees, while the temperature in a green area under trees may be 23 degrees.

Large shopping centres with extensive car parks are common potential heat island locations, Tamm said, citing the area around Viru Centre as one example. Critical areas can also be smaller spaces within a single city block that people pass through frequently.

Such conditions can cause heat stress, particularly for children, older people, those with chronic illnesses and people who work outdoors. Tamm said working in these conditions could even be dangerous.

Rubber surfaces at sports fields can also become very hot. Tamm recommended choosing playgrounds with trees nearby.

She said Tallinn has a considerable amount of tall vegetation, which helps. Nature-based solutions can reduce heat islands, but different aspects must be considered together when designing an area. Trees with large canopies help cool cities and ease people’s experience of hot weather.

Tamm also criticised the renovation of large central squares in European cities where little attention has been paid to creating shaded areas. During very hot weather, she advised people to avoid going outside at midday, cover their heads, wear light-coloured clothing and drink enough water.