Environmental Engineering Reference
In-Depth Information
As with previous human-microbe transitions, a new state of equilibrium
may lie ahead. However, it certainly will not entail a world that is free of
infectious diseases. Any future sustainable human ecology will have to come
to terms with the need for, and hence the needs of, the microbial species that
help to make up the interdependent system of Life on Earth.
Let us explore this ecological dimension further, especially in relation to
our growing impact on the world's environment. This dimension refers to
the larger-scale population-level changes, mentioned above, that exert the
important long-term influences on the patterns of disease and survival in
populations.
Changes in human ecology, environmental impacts and risks of disease
As we have seen above, a succession of profound changes in human ecology
has occurred over the past one hundred centuries, from the time that some
of our hunter-gatherer forebears began to seek out more secure sources of
food via the early processes of farming and herding. Debate continues about
the reasons for that radical change in the primitive human economy, but its
immediate consequence was indisputable: the local carrying capacity of the
environment was increased via this human intervention, and agrarian popu-
lations duly expanded. The main changes in human ecology over the
ensuing 10 000 years have been particularly in food production, social struc-
tures, urban living, industrialisation, reproductive behaviour, and, now,
demographic profile (as populations undergo an unprecedented ageing).
The career of
, viewed at the global scale, has now reached a
critical juncture in another very important respect (Raven 2002). Population
numbers have quadrupled over the past century; the scale of economic activ-
ity has increased approximately twentyfold over the same period; and, con-
sequently, we have inadvertently begun to change the conditions of life on
earth by altering the global climate, depleting stratospheric ozone, extin-
guishing whole species and their local populations, and damaging the food-
producing ecosystems on land and at sea. These global environmental
changes, unprecedented in human experience, are an unavoidable result of,
jointly, these increases in the size of the human population and in the inten-
sity and type of economic activity.
There has been an increasing awareness of the growth in size of human-
kind's 'ecological footprint' in recent decades. The metaphor refers to the
fact that a typical modern community depends on a very large area of Earth's
Homo sapiens
