The Value of Long-Term Assessment of Restoration: Support from a Seagrass Investigation

The importance of judging success of restoration studies over extended time periods has been repeatedly voiced but convincing information to justify increased monitoring is generally unavailable. Building on Bell et al. (2008), we investigated the development of areal coverage of the seagrass, Halodule wrightii, as a metric for assessing the outcome of a restoration effort conducted near Tampa Bay, Florida, U.S.A., over 7 years, thereby expanding the timescale over which a subtropical seagrass restoration project was evaluated for success. In each of 12 plots, 500 planting units of H. wrightii were introduced in 2002, and the seagrass cover level documented annually through 2009. Although only low-moderate levels of H. wrightii cover were recorded after 3 years, a rapid increase to high coverage levels was evident in many plots after 2006 and sustained through 2009. Plots that supported only low levels of seagrass cover initially remained poor performers, 4-7years post-planting. By 2008, substantial seagrass spillover, contiguous with over 75% of plots, was recorded. When both within-plot coverage and spillover were considered, seagrass restoration success was attained 6 years after initiation. Our findings provide an example of comparatively longer-term monitoring of a restoration effort leading to reversal of an earlier evaluation of project success. Moreover, unique information on H. wrightii temporal dynamics emerged from the 7 year study, further illustrating the value of long-term assessment of restoration. Extending the duration of post-planting surveys of seagrass coverage may address multiple needs as it advances the field of seagrass restoration.