This book draws lessons from ecological succession theory to inform ecological restoration, stating that: “restoration is fundamentally the management of succession” [Walker 2007: vi]. The latter is the natural process by which plants first colonize “new” land (post landslide, glacial retreat or volcanic eruption, for example) or degraded land, and over time develop into mature ecosystems through a series of changing plant communities. Ecological restoration is a human-led initiative to restore functioning ecosystems, or at least vegetation, on land degraded through human activity. The ultimate goal of restoration is to “establish a self-sufficient ecosystem that requires minimal or no continuing human inputs in order to provide a continuing supply of goods and services” [Hobbs 2007: 177].
Effective ecosystem restoration requires ecological knowledge. Likewise, the outcomes of such projects demonstrate our comprehension, or lack thereof, of ecological concepts: “Restoration is the acid test of our ability to understand not only how ecosystems are assembled and held together but also how they change over time” [Walker 2007: vi]. The authors contend, however, that restoration projects are more often guided by engineering, horticulture, and agronomy than by ecology. Aiming to clarify the ways in which ecological succession theory can and should inform restoration, this book poses the question: “What is the minimum amount of biophysical and successional information needed to restore a specific landscape or area” [Walker 2007b: 2]?
Succession comprises many ecological processes that underpin all ecological restoration and ecological restoration is a manipulation of these processes to achieve its goals. This means it is essential to understand how succession operates, and when and how to manipulate it [Prach 2007: 121].
Restoration can explicitly embrace a hands-off approach, where land is simply left to repair itself through natural ecological succession. On the other hand, understanding the successional process allows manipulation of various stages to speed up the process. For example, in the first stage of primary succession “winds deposit dust, pollen, seeds, and insects crucial to reducing infertility” [del Moral 2007: 23], on bare, inhospitable ground. Tough pioneer plants are able to establish then create shade, trap sediment, and deposit organic matter when they die, creating slightly better conditions for the next wave of colonizing plants. To mimic this first stage of site “amelioration”, the site can be physically manipulated by reshaping the ground for improved drainage or adding organic matter, for example.
Biological manipulation involves sowing or planting local/native varieties of later successional species that may not be otherwise present in the area due to human transformation of the broader landscape. While earlier successional species tend to have small, easily transported seeds, the later successional species (such as large canopy trees) that are often the target of restoration efforts often have large, less mobile seeds. Thus, if those plants are not present in the immediate environment as seed stock, they may never establish in the restored site without human assistance.
Del Moral, Roger, Lawrence R. Walker & Jan P. Bakker, 2007, Insights gained from succession for the restoration of landscape structure and function, Linking Restoration and Ecological Succession, Walker, Walker & Hobbs (eds), Springer Series on Environmental Management.
Hobbs, Richard J., Lawrence Walker & Joe Walker, 2007, Integrating restoration and succession, Linking Restoration and Ecological Succession, Walker, Walker & Hobbs (eds), Springer Series on Environmental Management.
Prach, Karel, Rob Marrs, Petr Pysek & Rudy van Diggleen, 2007, Manipulation of succession, Linking Restoration and Ecological Succession, Walker, Walker & Hobbs (eds), Springer Series on Environmental Management.
Walker, Lawrence R., Joe Walker & Richard J. Hobbs, 2007, Linking Restoration and Ecological Succession, Walker, Walker & Hobbs (eds), Springer Series on Environmental Management.
Walker, Lawrence R., Joe Walker & Roger del Moral, 2007b, Forging a new alliance between succession and restoration, Linking Restoration and Ecological Succession, Walker, Walker & Hobbs (eds), Springer Series on Environmental Management.