Are We Destroying Our Insurance Policy? The Effects of Alien Invasion and Subsequent Restoration - Landscape Ecology for Sustainable Environment and Culture - page 344

Fig. 16.17 The last remaining functional palmiet wetlands and peat beds in the Kromme River,
Eastern Cape, South Africa. The wetlands would have historically covered the floodplains of the
Kromme Riverbed, but have largely been removed in favor of agriculture
16.3.2.6 Rate of Spread of Black Wattle
The most dramatic increase in Black Wattle invasion is 10.37 ha during the period
1986-2007 (Fig. 16.21 ). However this is also the greatest time-step, with 24 years
between the respective aerial photographs.
The rate of invasion was greatest in the period between 1954 and 1969 at about
96 ha/a, which was its initial invasion phase. After this time, the invasion
ratesslowed to 12 ha/a perhaps indicating some threshold was reached. Between
1986 and 2007 the rate of invasion increases again to 43 ha/a, possibly indicating
the stage when began to invade old lands (Table 16.2 ).
16.3.2.7 Effectiveness of Mitigation Attempts: Rate of Clearing by
Working for Water
Working for Water began alien clearing in the Kromme Catchment in 1996. The
control programme involves an initial treatments followed by several, sometimes