Environmental Engineering Reference
In-Depth Information
technical innovation, the progress of economic development, changes in per capita
consumption, and the degree of readiness to forgo some material advances in order
to preserve the biosphere's irreplaceable services will be among the most obvious
factors on the list of technical, economic, and social factors that will determine the
eventual balance between the biosphere and modern civilization. If current appro-
priations were already as high as 35%-45%, then future harvest gains would push
them easily past the 50% mark, leaving less than half of the Earth's primary pro-
ductivity outside human reach and imperiling the provision of many environmental
services. Even if the actual claim is still no more than 20%, its qualitative impact
has already been substantial (Millennium Ecosystem Assessment 2005), and it would
be desirable not only to prevent its further expansion but to achieve its gradual
reduction.
Assessing the likely trajectories of all major socioeconomic factors in some detail
could be a topic for a number of topics: in closing this one I will briel y concentrate
only on the two categories of human action that will most directly affect the bio-
sphere's productivity and storage, the future rate of vegetation losses and the level
of agricultural output. More correctly, the i rst concern is with the net effect of two
countervailing trends: on one hand, the continuing deforestation and conversions
of other natural ecosystems to farmland and urban and industrial uses, harvests of
fuelwood and roundwood, and new liquid and gaseous biofuels; on the other hand,
continuing afforestation, more effective protection of existing forests, grasslands,
and wetlands (in parks, reservations, or carefully managed areas), and natural rec-
lamation of previously cultivated landscapes.
The only development that could slow down or even reverse the European, North
American, or Japanese forest expansion would be the (unlikely) large-scale conver-
sion of marginal farmland and currently forested land to biofuel plantations. In
contrast, the best outcome in most tropical and some subtropical countries would
be to have slower rates of deforestation and larger areas of remaining forests put
under effective protection: that the overall net loss of forest phytomass will be most
likely considerably lower during the next 50 years than it was during the past half
century is obviously welcome, but in light of a still high absolute reduction (most
likely in excess of 500 Mt C/year), it still remains a matter of serious concern because
primary forests are irreplaceable repositories of tropical biodiversity (Gibson et al.
2011). On the other hand, it has now become clearer that productivity is a poor
predictor of plant species richness (Adler et al. 2011), and hence the loss of some
highly productive forests may not be associated with a similarly high loss of
biodiversity.
