Environmental Engineering Reference
In-Depth Information
(anthropogenic biomes), where the processes are
primarily
(their emphasis) a func-
tion of human populations and their ecosystem interactions (land use)—or, as
they put it, “nature is now embedded within human systems.” They identify 18 dif-
ferent categories, with more than 40% of all people living in the urban anthrome
and another 40% living in six village anthromes. They claim not only that the
anthromes now cover more than 75% of all ice-free land but that they incorporate
90% of terrestrial NPP.
Even more astonishingly, Ellis and Ramankutty (2008) state that the share of
global NPP taking place in i ve anthromes in the croplands category is as high as
in two forested anthromes (populated and remote forests, in their classii cation),
namely, about 32%. This high share is explained by the fact that all natural growth
within areas affected by humans falls into one of the i ve anthrome categories, as
well as by the fact that the anthromes are the creations of computerized classii ca-
tion. Grid cells are i rst separated into “wild” and “anthropogenic” categories (based
on land-use features), and the latter are then stratii ed into population density classes
and assigned to one of the 18 anthromes that contain varying combination of land
uses and land covers.
Obviously, different criteria and different assumptions could produce differently
biased outcomes than these anthromic mosaics; one need only check the highest
available resolution of this classii cation (available at http://ecotope.org/anthromes/
v2/maps/a2000) for an area with whose land cover one is very familiar, and one
will be astounded by the degree of misattribution (forests labeled cropland, crop-
lands labeled residential area) and by misleading classii cations. The anthromic
mapping classii es about 85% of the city I live in as “dense settlements,” the rest
as “residential rainfed croplands.” But Winnipeg contains one of the largest urban
“forests” in the temperate zone, with an estimated eight million trees (along the Red
and Assiniboine Rivers, in extensive parks, and in street and residential plantings),
including the largest number of surviving American elms (about 160,000), trees
that have been destroyed elsewhere in North America by
Ophiostoma ulmi
(City
of Winnipeg 2011).
My very conservative calculations put the total standing phytomass of Winnipeg's
trees at 1.2 Mt C, prorated to about 40 t C/ha of actually settled area within the
city's boundary. That phytomass density is only slightly lower than the expected
aboveground storage in a boreal semiarid deciduous forest (Luyssaert et al. 2007),
and Winnipeg could be thus be “anthromically” classii ed as “residential wood-
lands” rather than as “dense settlements.” This urban forest is overwhelmingly a
result of deliberate planting and continuous management, but its phytomass density
