FIGURE 4–6 Coral reefs contain ecological diversity as extensive as that found in tropical forests. Photo by G.Carleton Ray.

are productive and diverse, but they are not nearly as useful for food production as are temperate seas, where schooling fishes predominate and can be easily caught over extensive banks and shelves. There is a negative correlation between diversity and productivity in these cases. By analogy, farming on land is most productive for humans when systems are simplified. One of the greatest challenges for marine science is the prediction of consequences that would result from the loss of diversity in the increasing number of coastal systems that are being farmed through aquaculture. Will this lead to the loss of the characteristic diversity of coastal systems and thus to the loss of system predictability? This is the danger of not heeding Lovelock’s warning quoted above.

Perhaps the greatest challenge of all lies in determining which characteristic species contribute most to their ecosystem, to productivity, to predictability. Are some species more essential than others from a functional, ecological point of view? In the present state of our ignorance, an attempt to answer this might lead to some nasty choices. Surely some species are more important to their ecosystems than are others, as indicators of ecological processes or as keystones that influence community structure. But which are these? We know pitifully few of them for coastal and ocean systems. So when some decision-maker asks which species might be sacrificed, we cannot say. The immense diversity of life seems simply redundant to many who are in the position of having to decide about environmental matters—and we might have to admit that some species may indeed be redundant. But when asked to identify such redundancies, we may react like the young Mozart when