Chapter 23
Environmental change
1. Introduction
In the course of Earth's history numerous changes in the climate, sea level, vegetation
cover, animal population, soils, and landforms have taken place (Goudie, 1992), but it is
Quaternary time during which those constant environmental changes, which occasionally
take place in short spans, can be detected with more accuracy. In recent times, from the
geomorphological perspective these environmental changes are due to the three basic
causes that are geological, climatic and anthropic. The difficulty in knowing in detail the
factors that trigger these changes derives from the interactions among causes, as often they
act jointly, and it is therefore, difficult to interpret the contribution of each separate one
to the environmental change.
Geological environmental change is mainly due to neotectonic activity (Figure 23.1),
which is significant in areas located on active plate margins, where isostatic compensation
and relative displacement between plates of the lithosphere produce significant relief
modifications. For example, the deserts of mountains and depressions of the western USA
and central Asia (Mabbutt, 1977) that show large crustal instability are affected by such
activity. On the other hand, shield and platform deserts, such as the Sahara, India, and
Australia, are not significantly influenced by endogenic causes. On the latter continent
climate change can be more easily studied in the absence of tectonics.
Even though humans have dwelt on Earth for about 3 million years, their interaction
with the environment began to be significant only about 10,000 years ago with the
agricultural revolution, and especially with the more recent industrial and medical
revolutions (Goudie, 1981b). Humans can significantly affect the vegetation, fauna, soil,
water, and climate, which is why is they are considered a geomorphological agent
(Dov Nir, 1983), as well as the fact that human activity modifies the Earth's surface
(Figure 23.2) and interferes with non-human geomorphological processes.
Climate change seems familiar, because we are used to temporal fluctuations in
precipitation and temperature in our lifetime. In addition to these short-term variations,
longer and deeper fluctuations occur. These features are illustrated in the different climate
change scales shown by Goudie (1992) and Boulton (1993). In those scales climate
fluctuations are reflected from intervals of tens of years to the scale of geological time
(Figure 23.3).
Long-term climate changes (Goodess et al., 1992) become apparent in temporal scales
above 20,000 years, as with Quaternary glaciations. These changes are produced by
modifications outside of the climate system, such as changes in the geometry of the orbit of
the Earth around the sun (Milankovitch cycles). Short-term climate changes range from
100 to 20,000 years. They are related in part to external causes, but some mechanisms can
Environmental change
1. Introduction
In the course of Earth's history numerous changes in the climate, sea level, vegetation
cover, animal population, soils, and landforms have taken place (Goudie, 1992), but it is
Quaternary time during which those constant environmental changes, which occasionally
take place in short spans, can be detected with more accuracy. In recent times, from the
geomorphological perspective these environmental changes are due to the three basic
causes that are geological, climatic and anthropic. The difficulty in knowing in detail the
factors that trigger these changes derives from the interactions among causes, as often they
act jointly, and it is therefore, difficult to interpret the contribution of each separate one
to the environmental change.
Geological environmental change is mainly due to neotectonic activity (Figure 23.1),
which is significant in areas located on active plate margins, where isostatic compensation
and relative displacement between plates of the lithosphere produce significant relief
modifications. For example, the deserts of mountains and depressions of the western USA
and central Asia (Mabbutt, 1977) that show large crustal instability are affected by such
activity. On the other hand, shield and platform deserts, such as the Sahara, India, and
Australia, are not significantly influenced by endogenic causes. On the latter continent
climate change can be more easily studied in the absence of tectonics.
Even though humans have dwelt on Earth for about 3 million years, their interaction
with the environment began to be significant only about 10,000 years ago with the
agricultural revolution, and especially with the more recent industrial and medical
revolutions (Goudie, 1981b). Humans can significantly affect the vegetation, fauna, soil,
water, and climate, which is why is they are considered a geomorphological agent
(Dov Nir, 1983), as well as the fact that human activity modifies the Earth's surface
(Figure 23.2) and interferes with non-human geomorphological processes.
Climate change seems familiar, because we are used to temporal fluctuations in
precipitation and temperature in our lifetime. In addition to these short-term variations,
longer and deeper fluctuations occur. These features are illustrated in the different climate
change scales shown by Goudie (1992) and Boulton (1993). In those scales climate
fluctuations are reflected from intervals of tens of years to the scale of geological time
(Figure 23.3).
Long-term climate changes (Goodess et al., 1992) become apparent in temporal scales
above 20,000 years, as with Quaternary glaciations. These changes are produced by
modifications outside of the climate system, such as changes in the geometry of the orbit of
the Earth around the sun (Milankovitch cycles). Short-term climate changes range from
100 to 20,000 years. They are related in part to external causes, but some mechanisms can