Timeframe for assessing whether a site is "restored"

In Phase 1 you indicate that “While both tracks will ultimately be judged against the same overall goal – restoration of the greatest number of hectares of coral in a two-year period – the main difference between the two tracks will be the criteria for determining whether a hectare of coral is in fact, restored.”
This leads one to ask when and how one can judge at what point a denuded/degraded reef has been “restored”. Using Society for Ecological Restoration guidelines, the target for any reef restoration is set by a “reference ecosystem” (see McDonald et al. 2016) based on one or more relatively intact reference sites or what the target site was like before degradation (possibly with some allowance for environmental change). Natural recovery of reefs from major disturbances such as tropical cyclones or ENSO related warming events seems to take 10-15 years (e.g. reefs in areas with low local anthropogenic pressures such at Maldives or Palau recovering from the 1998 mass-bleaching). Waiting a decade or so to reach an unarguably restored state similar to the “reference ecosystem” does not seem practical, so at what point could one argue that a restoration intervention has been successful? What criteria could indicate that the reef ecosystem is potentially (barring major disturbances) on a sustainable trajectory towards recovery?
I think most people would agree that if you have (1) sexually/asexually produced coral propagules that are mature and spawning, and (2) there is evidence of adequate recruitment of juvenile corals, then you have a functioning self-sustaining ecosystem that is on track to recovery and will within several years (barring accidents) be “restored”.
How long might be needed? A few corals have been reared from egg to maturity in 3 years and for several species this has been achieved in 4-5 years. This suggests that at least for sexual propagation methods, the earliest that success can be judged is likely to be around 5 years into the project.
How does one evaluate “adequate” recruitment? The healthy “reference site” will give an indication of natural levels of coral recruitment that support the sustainability/persistence of the target coral community. With recruitment at similar levels to the reference site and locally spawning adults of key coral species, there seems a persuasive case that the restoration is “successful” or at least on track to success.
However, if there is no evidence that the propagules represent a sustainable community that is contributing to the next generation (as demonstrated by spawning and recruitment) then it is hard to see how a functioning ecosystem has been “restored”. All that has been achieved is the temporary addition of some live coral material to a reef. Surely, only once the life cycle is shown to be complete (“closing the circle”, sensu Guest et al. 2014 in Coral Reefs) at the restoration site can one claim that the intervention is on a trajectory towards “restoration”?
Is a two-year timeframe sufficient?

@aje191 Thank you for the comment. Yes, completely agree that true restoration from an ecosystem standpoint may not be achieved within the timeframe of a prize. However if we’re looking at restoration in the context of a prize, or rather “on track to restoration” within the timeframe, any thoughts on the parameters we may be able to judge that success? For the asexual track, many have mentioned that an increase in live coral cover would be the most adequate, considering regional differences in species density and availability; and for larval, achieving a certain colony density of some determined size per square meter. Any further thoughts on this and what those specific parameters might be?

Hi Anupa, a very good question. Any restoration project is trying to restore an ecosystem back to some target “reference” ecosystem – the first “key concept” in McDonald et al. 2016. International standards for the practice of ecological restoration – including principles and key concepts (published by the Society for Ecological Restoration). Each reef site is likely to be very different and one can only really judge success or progress towards success based on the a priori objectives of the rehabilitation project and the baseline starting point at the site. The reference ecosystem provides you with an example of what your dominant species are, the target colony density and the approximate % live coral cover that might be expected once the site has “recovered”. In theory if each participant stated their goals – based on their local reference ecosystem – then progress towards those goals could be judged, though this might be difficult after only two years.
You mention that many have talked about increase in live coral cover as a measure of success. If your reference ecosystem is dominated by a few species of slow-growing massive or sub-massive corals, which are likely to be relatively long-lived (decades to hundreds of years) and resistant to bleaching, and thus one would think worth considerable effort in restoring, the competition is stacked against you if % cover is the measure of success. Only if your reference ecosystem consists of fast-growing relatively short-lived branching species (e.g. Acropora) that are also relatively susceptible to bleaching and disease will you be likely to win. To game the competition you could attach fragments at abnormally high densities but the fast growers are always likely to win if costs are taken into account.
In a number of countries I’ve seen substantial areas of reef almost entirely dominated by only one or two species. A successful restoration would result if the one or two species were restored. But how do you compare such a site to one where the assemblage is much more diverse? Each site has to be judged in terms of progress towards goals that are dictated by the reference ecosystem the project is attempting to return to. Thus a perfectly valid and laudable aim would be to restore a shallow reef area in the Caribbean that had previously supported Acropora palmata but lost this due to disease or other disturbances. Such sites are often completely dominated by Elkhorn coral so restoring that single species would seem a reasonable goal (an undegraded reference site would provide data on likely colony density needed, natural levels of recruitment etc.). Progress towards that goal (based on some density of live colonies derived from the reference ecosystem) using asexual or sexual propagation techniques and relative cost-effectiveness can be judged but I cannot see how a single figure such as % live coral cover [after two years] can be used.

Hi @aje191! I have limited knowledge about the time frame that coral restoration has taken in the past. But, I do believe a two year time frame is sufficient because at least if you can push teams to make the most progress they can under time restraints. I believe giving an extension to multiple teams after that period will be realistic as well, as projects like this will have more support and funding over these next two yeas. I think it would be smart for the teams to set up systems along with their plans to receive crowd funding or outside capital to drive their exploration in their projects. But I think after these 2 years, teams will come up with multiple viable ways to potential restore the reefs. LETS RESTORE the REEFS ??