ENVIRONMENTAL-EFFECTS OF MINING COASTAL DUNES - CONJECTURES AND REFUTATIONS

The conjectured effects of mining coastal dunes in northeast South Afr ica were that mining would cause irreparable damage, homogenise soils, destroy litter and reduce biodiversity that rehabilitation would not restore. It was further conjectured that succession to forest climax t akes centuries, that post-mining vegetation recovery is a function of distance from the seashore where refugia exist and that ecologists can not predict local succession. The conjectures were tested using 44 unm ined and 62 mined sample plots. Mined and unmined soils could not be d istinguished reliably. The depth of the organic layer at the soil surf ace was a function of time since disturbance and soil density. Species richness did not differ between mined and unmined land. The upper asy mptote of species richness was projected to be reached in 28 to 40 yea rs post-mining, and convergence on forest climax species composition i n 54 to 70 years. Distance from the seashore was confounded with other variables that better explained vegetation recovery. The key multiple regressions developed to test the conjectures accounted individually for 45% or more of the variation in the dependent variables, and had o verall P values from <0.01 to <0.001. Randomly assigned subsets of the database yielded statistically indistinguishable patterns, implying t hat inferences were robust.