Valuation of health benefits of green-blue areas for the purpose of ecosystem accounting: a pilot in Flanders, Belgium

In recent years, a vast amount of scientific literature has highlighted the benefits of nearby green space for physical and mental health, but the large variation in scope, methods and indicators used in these studies hampers the assessment of these benefits in the context of natural capital accounting. To our knowledge, this paper is one of the first studies to quantify and value these benefits in the context of natural capital accounting. A method was developed and applied to the Flemish Region in Belgium for 2013 and 2016.

The physical supply and use accounts for health are based on a set of selected dose-effect relationships that quantify the impact of the availability of greenspace on seven specific indicators for physical and mental health, including mortality, cardio-vascular diseases, diabetes and depression. The indicator for green-blue areas is the percentage of green-blue areas in total land use, calculated for 0.5, 1 and 3 km radius from the residence, based on detailed land-use maps (10 m x 10 m) for Flanders, Belgium. The base-line data for mortality and illness are average data for the Flemish Region. These health impacts are weighted using Daly's (disability-adjusted life years) and aggregated. The total health benefits due to the availability of green-blue areas for the total Flemish population was estimated at almost 85,000 DALYs. This is 27% of the estimated total burden of disease in Flanders in 2016 for the seven selected diseases.

The monetary accounts are based on a detailed assessment for mortality and morbidity of three different cost components, i.e. avoided medical costs (e.g. hospitalisation) and avoided absenteeism and welfare loss due to suffering and reduced life expectancy. Productivity gains from avoided absenteeism is valued, based on statistics on absenteeism for specific diseases for and labour market data from Belgium and account for 52% of the total monetary value of green spaces. Cost of illness is valued, based on market data and illness specific studies for Belgium or Europe and account for 36% of total values. Welfare gains from increased life expectancy are valued on the basis of European studies for the VOLY (value of a life year lost), based on the simulated exchange value for the willingness-to-pay for increased life expectancy. This accounts for 12% of the total monetary value of green space. The total monetary benefits amount to 464 Euro per inhabitant per year or 3 billion Euro per year for Flanders. This corresponds to 1.3% of the GDP, which reflects the importance of these benefits.

The methodology is incomplete as not all health indicators are covered, mainly due to a lack of dose-effect relationships. The research priority for potential users of the accounts is a better indicator for contact with green space that does differentiate between ecosystems, their quality, accessibility or their use. This requires more systematic health impact studies that take these elements into account, as well as more systematic data on the daily use of green space by citizens. In the meantime, an additional set of condition accounts on these elements can be used, especially to follow changes in quality and use of green-blue areas over time.