7. Theory and Practice of Biodiversity
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other variable. A science of biodiversity must incorporate the impact of humans on
the landscape as well as their behavior vis-a-vis the environment, studied until now
almost exclusively by anthropologists.
4 Impact of Human Activities on Ecosystem
Function
Yet not everybody agrees that these transformations are serious or that they can
have dire consequences for the survival of the human species. Global warming is
denied by some, or its consequences are represented as benign; loss of biodiversity
is considered inconsequential to human welfare, and those of us who worry about it
are called alarmist; and chemical contamination is not taken seriously. As long as
there is doubt regarding the impact of human activities there will be differences of
opinion, and people who always are reluctant to change their behavior will use
these varying opinions to rationalize their actions. A rigorous, unbiased, and mechanistic science of biodiversity can help resolve these differences.
Agriculture is one of the principal agents of landscape transformation and is a
good example of the dilemmas faced by individuals and society in regard to ecosystem change. Let us therefore briefly analyze ecosystem function in relation to agriculture and assess the evidence regarding the significance of the changes taking
place.
When our ancestors adopted agriculture they contracted a Faustian bargain. In
exchange for a new and more reliable source of sustenance, not only would their
toil increase, but they had to bear the consequences of the transformation of the
land they plowed and the plants and animals they grew. Hunter-gatherers had appropriated over many previous millennia some of the products of nature - fruits,
seeds, game - changing only minimally the characteristics of the ecosystem that
produced these resources. However, agriculturalists and pastoralists purposefully
increased the abundance of some species, and eliminated others. Furthermore, with
time they also affected the characteristics of the crops and domestic animals they
maintaincd to the point that they no longer can reproduce by themselves, or compete with the native vegetation or fauna. A case in point IS the wheat plant. Hexaploid Triticum aestivum, the most widespread plant in the world, is not known in
the wild and is incapable of reproducing by itself, and would disappear from this
planet if farmers stopped planting it. Similar considerations apply to cultivated rice
and maize, the plants that together with wheat constitute 50% of the food intake of
humankind. Yet, while humans have assumed the responsibility of being the administrators of the evolution and reproduction of their domestic plants and animals, they have not assumed the same degree of responsibility in relation to the
physical characteristics of the agro-ecosystems where these plants and animals live,
resulting in enormous losses of topsoil.
Erosion is the most serious and costly of the negative effects of modern agriculture. Soil that is lost is difficult to recover, and restoring degraded soils is expensive
111
other variable. A science of biodiversity must incorporate the impact of humans on
the landscape as well as their behavior vis-a-vis the environment, studied until now
almost exclusively by anthropologists.
4 Impact of Human Activities on Ecosystem
Function
Yet not everybody agrees that these transformations are serious or that they can
have dire consequences for the survival of the human species. Global warming is
denied by some, or its consequences are represented as benign; loss of biodiversity
is considered inconsequential to human welfare, and those of us who worry about it
are called alarmist; and chemical contamination is not taken seriously. As long as
there is doubt regarding the impact of human activities there will be differences of
opinion, and people who always are reluctant to change their behavior will use
these varying opinions to rationalize their actions. A rigorous, unbiased, and mechanistic science of biodiversity can help resolve these differences.
Agriculture is one of the principal agents of landscape transformation and is a
good example of the dilemmas faced by individuals and society in regard to ecosystem change. Let us therefore briefly analyze ecosystem function in relation to agriculture and assess the evidence regarding the significance of the changes taking
place.
When our ancestors adopted agriculture they contracted a Faustian bargain. In
exchange for a new and more reliable source of sustenance, not only would their
toil increase, but they had to bear the consequences of the transformation of the
land they plowed and the plants and animals they grew. Hunter-gatherers had appropriated over many previous millennia some of the products of nature - fruits,
seeds, game - changing only minimally the characteristics of the ecosystem that
produced these resources. However, agriculturalists and pastoralists purposefully
increased the abundance of some species, and eliminated others. Furthermore, with
time they also affected the characteristics of the crops and domestic animals they
maintaincd to the point that they no longer can reproduce by themselves, or compete with the native vegetation or fauna. A case in point IS the wheat plant. Hexaploid Triticum aestivum, the most widespread plant in the world, is not known in
the wild and is incapable of reproducing by itself, and would disappear from this
planet if farmers stopped planting it. Similar considerations apply to cultivated rice
and maize, the plants that together with wheat constitute 50% of the food intake of
humankind. Yet, while humans have assumed the responsibility of being the administrators of the evolution and reproduction of their domestic plants and animals, they have not assumed the same degree of responsibility in relation to the
physical characteristics of the agro-ecosystems where these plants and animals live,
resulting in enormous losses of topsoil.
Erosion is the most serious and costly of the negative effects of modern agriculture. Soil that is lost is difficult to recover, and restoring degraded soils is expensive