2.3.4 Environmental Benefits

Our parks and open spaces perform specific environmental services for the city. The generation of carbon dioxide through human activities, in particular the use of fossil fuels, is recognised as a leading contributor to greenhouse gases and global warming. In Dublin the CO2 emissions per head of population is 9.72 tonnes (The Green City Index), which is higher than the European average for cities.

Balancing Dublin’s carbon footprint to significantly reduce our above average CO2 emission is assisted by city greening. City vegetation, through the process of photosynthesis, actively takes in carbon dioxide and stores it, which is known as carbon sequestration. Air pollution is mitigated in urban areas by green spaces providing a buffer from sources of air pollution, as well as filtering out components of this pollution. Particulate matter (PM), for example, which is known to be produced by vehicular traffic and causes breathing problems such as asthma, is filtered by tree leaves. Research in London indicates that between 850 and 2000 tonnes of PM10 (particles less than 10 microns in diameter) are filtered out per year by urban trees in the Greater London Authority.

Flooding is also a problem that the city experiences on a regular basis, both from coastal waters and during high rainfall periods. Impermeable surfaces, which are extensive within built-up areas (e.g. roofs, roads and pavement), produce unwanted water, which is directed to the sewer systems. The volume of water runoff during high rainfall periods can exceed the capacity of the system to drain it effectively, resulting in flooding. In addition, rising sea levels, together with tidal and wind events, can lead to coastal flooding along Dublin’s shoreline.

Dublin’s green spaces help to alleviate the problem by providing permeable surfaces, thus allowing natural drainage as well as providing space to alleviate both coastal flooding and river flooding. Vegetation also helps to protect surfaces from washing away and by taking up water through the process of transpiration.

Improving the city’s resilience to high rainfall events can be assisted through improved city greening initiatives, such as planting on road corridors and buildings.