Marcelino Fuentes at Biopolitical makes a point that punctuates the previous post on "The risks of faith based science".

From the Asian tsunami to Katrina, the message should be obvious: where they still exist, we must protect our coastal ecosystems; where they do not (as in much of our Gulf coast) we must reconstruct them.

The message is not obvious because we don't have a quantitative measure of the benefits and the costs, including foregone opportunities, of maintaining and reconstructing all coastal ecosystems. One can advocate the preservation or reconstruction of coastal ecosystems - all of them, and regardless of costs - only by assuming that they have effectively infinite benefits.

If protection against disasters has infinite value we should not stop at maintaining and reconstructing coastal ecosystems. We should invest enormous (just a little less of infinite) resources in designing and erecting protections that are even more effective than natural ecosystems.

Actually, protection against disasters has, like everything else, finite value. Moreover, at the margin this value is effectively zero.

This is a clear case of arguments "generated by people who knew what conclusion they wanted and were doing their best to fudge up reasons to believe it". Coastal defenses against storms and waves can take many forms. The Dutch and even the British have shown this with mechanical barriers. An argument for the use of mangroves needs to establish that this is a better way considering all factors including costs as well as benefits.

Nations in the area, such as India, have already spent decades and millions trying to regenerate mangroves. They've had limited success for all the common reasons. It's a massive task, there are competing values and objectives and a great deal of the funds and energy is siphoned off by the invariant corruption and graft that accompanies such efforts, as well as the laughable ineffectiveness of government style programs. (Recall recent criticism of the amount of relief money squandered on UN overhead rather than tsunami relief, and the comparative ineffectiveness of the US Army Corp of Engineers compared to private companies in post-Katrina cleanup).

We could work ourselves into a snit about the impediments to efforts such as mangrove regneration, and make foolish comments about political will yada yada, but it is better to reason from evidence and make useful policy prescriptions. Faith doesn't get it in these matters. Besides, how fast can those mangroves scramble uphill as sea level rises 20 feet when the ice caps melt;-)