The 386 European cities accounted for 170.6 million inhabitants in 2001 (34% of Europe's population). Green space coverage varied markedly, averaging 18.6 per cent and ranging from 1.9 (Reggio di Calabria, Italy) to 46 (Ferrol, Spain) per cent. This coverage showed a clear central tendency, and its frequency distribution among cities was not distinguishable from a normal distribution (Kolmogorov–Smirnov Z
=0.172). Some 45.2 million people inhabited cities in the lowest quartile (2–13%) of green space coverage, indicating limited green space availability for a significant proportion of Europe's population. Proportional green space coverage in the cities increased with latitude (r
<0.001; ). Per capita
green space provision varied by two orders of magnitude, from 3 to 4
per person in Cádiz, Fuenlabrada and Almería (Spain) and Reggio di Calabria (Italy) to more than 300
in Liège (Belgium), Oulu (Finland) and Valenciennes (France). This variation formed a clear spatial pattern at country level, with lowest provision in the south and east of Europe, increasing to the north and northwest ().
Figure 1 Urban green space coverage in Europe. Points representing cities are coloured according to proportional coverage by urban green space within the city. Country polygons are coloured according to per capita green space provision for its urban inhabitants. (more ...)
The slope of the relationship between city area and human population size was not distinguishable from unity (β=0.986, 95% CI=0.939–1.036, p=0.584; a); larger cities were no more or less densely populated than smaller cities. By contrast, green space area increased more rapidly than city area, the relationship between the two variables showing a slope significantly greater than unity (β=1.179, 95% CI=1.127–1.233, p<0.001; b). Thus, cities differing in area by an order of magnitude will have a 15-fold difference in green space area. Despite excellent fit by linear models, both relationships showed signs of weak nonlinearity, with values at low levels of city area tending towards the origin of the plots (). Generally then, cities large in area had greater green space coverage despite the fact that the human population density was similar to cities smaller in area.
Relationships between city area and (a) human population size (standardized major axis regression: r2=0.760, p<0.001) and (b) green space area (r2=0.802, p<0.001).
Among the 67 UK cities, human population size increased more rapidly than city area (β=1.057, 95% CI=1.008–1.107, p=0.021), and the slope of the relationship between the city area and the green space area did not differ significantly from unity (β=1.013, 95% CI=0.931–1.103, p=0.757). Green space provision in the UK therefore increased only at the same rate as city area, a bleaker picture than across Europe as a whole.
Across European cities, proportional green space coverage declined with increasing human population density (r=−0.350, n=386, p<0.001), although there was a weak ‘space-filling’ effect in the relationship driven by a decline in upper levels of coverage as density increased. In an ordinary least squares regression fitting linear and square terms for population density, both predictors were significant, with negative and positive slopes, respectively (p<0.001 in both cases). Thus, the decline in green space availability per capita accelerates with increasing population density. By contrast, the relationship between these two variables was not significant for the UK (r=−0.165, n=69, p=0.174), confirming that further increases in density in already compacted urban landscapes are not achieved by further reductions in green space provision.