Are We Destroying Our Insurance Policy? The Effects of Alien Invasion and Subsequent Restoration - Landscape Ecology for Sustainable Environment and Culture - page 337

Fig. 16.10 Annual precipitation in the upper Kromme from 1881 to 2007. The black stippled
line is the trend line for rainfall. The horizontal gray stippled line indicates the overall mean
rainfall per annum for this period (678 mm). Gray arrows indicate the occurrence of flood events
according to the historical record (which only begins in the late 1920s), larger arrows represent
larger floods
the lands productivity for agriculture or grazing. This process also destroys wetlands -
which in a healthy state provide many services to society.
Overall it appears as though annual rainfall has decreased, albeit not signifi-
cantly (R 2 = 0.071), over the past century (Fig. 16.10 ), with the seven lowest
rainfall years all occurring during the past 40 years. Furthermore, the annual
rainfall has not exceeded 823 mm in the last 30 years, compared with nineteen
times in the preceding century. It appears as though extreme rainfall events are
increasing in frequency, despite the fact that there is a decrease in annual rainfall
in the past 40 years.
16.3.2 Land-Use Changes
Over time, both productive and unproductive fynbos vegetation groups have
become degraded as a result of increasing grazing pressures and increases in fire