Restoring and maintaining the biological integrity of the system is the ultimate goal of the Lower Columbia River Estuary Program. Because each of the other priority issues has significant impacts on biological integrity, actions taken to address them will contribute to this overall goal. To sustain a biologically diverse community, the physical processes that support the system must be in balance. In the case of the Columbia River, good water quality and sufficient water quantity at the right times are keys to providing the aquatic environment necessary to support a diversity of native organisms. Diverse riverine habitat, including an abundance of functioning wetlands and riparian areas, are the other supports of this system.
Biological integrity is, in essence, the sum of all the parts of the natural system.
When any of these parts is out of balance, biological integrity is threatened. Although a healthy system can adjust to significant disturbances, overall integrity is compromised once the scales tip too far, to the point where the system can no longer support the life cycles of some native species. Tools to measure and define biological integrity are limited, and have not been extensively used in the Estuary Program study area. The river system is so large and observations regarding its condition are so varied that it is difficult to gain a full understanding of the status quo. Nevertheless, there is strong evidence to suggest that the biological integrity of the lower river and estuary is out of balance.