the restoration ecologist is interested in the structure or architecture of the original forest because of its ability to do things that cannot be done by degraded and eroded soils. The forest can build soils, control the capture and release of moisture, and regulate nutrient cycles. It can withstand climatic fluxes and perturbations, and critically important to the naturalist, it can support an enormous spectrum of life forms. The forest’s dimensions extend from the tree canopy to root depths often tens of meters below the soil surface.

In the hillside example, the structural, as distinct from the species-specific, restoration ecologist wants to build fertile soils, develop a water and nutrient regimen, and assemble an ecosystem that mimics the original structural integrity of the forest. The actual organisms selected to do the job may or may not be the original species. Often, the ecologist will seek out equivalent species of plants or animals that have secondary properties as well. For example, a tree species that is not adapted to the environment, but is highly valuable, provides an economic dimension to the process. Also the land restorer, like a farmer, will in most instances use a large array of biotechnologies and technological aids to orchestrate and even speed up successional and other biological processes. Sophisticated bioengineering is used to recreate the equivalent of hundreds of years of topsoil within a decade or two.

The mission of the two restoration ecologies can be quite different too. Structural ecologists are willing to tolerate wider margins of uncertainties and gaps in knowledge, thereby adopting a more applied viewpoint simply because they see the planetary environmental crisis as the backdrop against which they work. To reverse desertization and habitat destruction, it ultimately will be necessary to undertake ecological restoration on a vast, planetary scale. This means that the task cannot be guided by charity based on social conscience, since there isn’t enough of either even to finance or underwrite the required backup ecological research. It is hard to avoid the conclusion that if there is to be any meaningful change, restoration ecology will have to become quite simply a major economic activity. Just as the activity seeks to recreate the forest on the hill, it will also be expecting the hill to become a sustainable and environmentally enhancing economy. A goal will be the provision of a wide variety of marketable products as a by-product of the restoration process. This is an extremely ambitious objective for a young field of endeavor, but one that is essential to its widespread application.

Fortunately there exists, albeit widely scattered, the biological knowledge and field experience to build a science and practice of habitat recovery. This knowledge needs to have an ecological framework whose elements will be found in geology, climatology, agriculture, forestry, horticulture, aquaculture, limnology, research ecology, landscape architecture, and natural history, to name some of the more relevant fields of endeavor. There will also be a need to develop and adapt tools and machines for use in agriculture, earth moving, forestry, waste management, and process engineering.

Returning to our hypothetical example of the eroded hillside, the first step in the restoration process would be to arrest rapid rainwater runoff and to reduce erosion. Among the many approaches that can be taken are various tillage techniques, microcatchments, contouring, and land sculpturing to regulate water move-



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