Environmental Engineering Reference
In-Depth Information
More fundamentally, it is a concept whose consensual unambiguous formulation
is hardly possible, whose practical applications are made questionable by a number
of logical shortcomings, and whose application reduces many complex processes
to a single i gure. Like so many other indexes and global measures, it does tell us
something important, in this case about the human claim on the biosphere's primary
resource, but the published HANPP values are too uncertain, too dependent on the
concept's dei nition, and, perhaps most important, entirely devoid of any qualitative
connotation to offer a special insight or guidance.
Rather than using the latest data to produce a new version according to one of
the published HANPP procedures or creating yet another dei nition of appropriation
and offering a new range of global values, I will devote the following two sections
to fairly straightforward quantii cations of phytomass harvest and will do it in
two ways, by presenting rather comprehensive accounts of phytomass harvests at
the beginning of the twenty-i rst century and then by making more approximate
historical estimates in order to uncover some long-term trends, stressing the data
limitations as I proceed. For practical reasons I take up this exercise in two topical
sections, i rst presenting a detailed account of the phytomass needed to produce
food for seven billion people and then aggregating the best available information
on the harvests of woody phytomass.
Evolution of Terrestrial Food Harvests
Rough estimates of crop phytomass harvested on national and global levels are
not difi cult to make and, given a number of unavoidable approximations that
must be made (even in the case of countries with the best available statistics), they
may sufi ce to make an effective assessment of major phytomass l ows and their
long-term trends. The FAO's annual global collation of production statistics pro-
vides a readily accessible basis for global calculations whose overall error for major
crop categories is unlikely to be greater than 5%-10%. In the year 2000, the
global harvest of cereal food and feed grains (dominated by wheat, rice, corn,
sorghum, and barley) was nearly 2.1 Gt. Sugar crops (beet roots and sugarcane
stems) came second, with 1.5 Gt; the vegetable harvest (about 750 Mt) was more
than 50% higher than fruit production (about 470 Mt), while tubers (mainly white
and sweet potatoes and cassava) added about 700 Mt, oil crops (mostly soybeans,
peanuts, sunl ower, rape and sesame, olives, and oil palm fruits) about 100 Mt,
and leguminous grains (led by beans, lentils, and peas) more than 50 Mt (FAO
2011d).
