Modern sustainable city developments normally include plenty of green areas of parks and trees – and with good reason. Besides providing an aesthetic and recreational break from the urban lifestyle, they also form a carbon sink.
But their significance appears to be greater than that. A new study from the Universidad Nacional de Entre Ríos has found that streets with trees can be significantly cooler than trees without. The study conducted in the centre of Buenos Aires – where the streets are lined with highrise buildings and tend to be relatively narrow – found a difference of 3.2oC between two parallel streets, one with trees, the other without. When grassed areas are included, the difference can be even greater, up to 9oC the study found.
“Trees are essential when talking about heat islands and temperatures in cities,” according to the study’s director, María Silvia Carponi, of the University’s Agricultural Sciences faculty, in the February 24 edition of La Nacion newspaper.
Trees to save energy
The primary beneficiary of such a treed street would be the pedestrians, but there may be also some impact on the surrounding buildings and their need for air conditioning.
Air conditioners are major users of electricity and especially in developing countries, growing incomes have led to significant growth in air conditioning with a consequent impact on peak demand. In China, for example, sales of air conditioners have nearly doubled over the last 5 years. In 2013 alone there were 64 million units sold, more than eight times as many as were sold in the United States
In Mexico, a recent study from the Haas School of Business at the University of California Berkeley predicts there will be near universal saturation of air conditioning in all warm areas within just a few decades.
In Buenos Aires, many air conditioners tend to be old and energy inefficient and only in the last few years have energy efficient models been available. The situation has been further exacerbated by the absence of a culture of efficiency, due to low, highly subsidized energy prices. However, this will likely change under the current (new) government, which is stripping back these subsidies so that (in theory, at least) they will go to only those who really need them. (Aside, recent changes by the new government should also result in the first major investments in the networks in a decade.)
Steps to energy efficiency
It is likely that Buenos Aires microcentre’s streets have already gained some environmental improvements. In recent years there have been increasing restrictions on cars, bus routes have been moved out, bicycle lanes have been introduced and some streets have been pedestrianized. However, few of these have been treed.
It is never too late to put in trees, space permitting, and it is a combination of actions like this that make up energy efficiency, whose total impact is greater than the sum of their parts.