Posts Tagged ‘Herons’

The metrics debate: habitat for middle-aged great blue herons who don’t like shrimp?

Sunday, April 22nd, 2012

Whenever discussions on biodiversity offsets get technical, they either focus on legal and cost issues (if you’re paying) or on their underlying ecological reality (if you’re the regulator). Concerning the latter, the question is how you actually assess equivalence between what is lost on the one hand, and what is generated by the offset on the other? So it’s all about what and how you measure to assess those gains and losses – hence the metrics debate.

In his blog, Morgan Robertson exposes this issue as a “paradox”.

I’ve been thinking about this for a long time — in fact it seems like everything I’ve ever written boils down to “defining environmental commodities is HARD because ecology is complex and commodities need to be abstract”.

The paradox is that the metrics must strike a difficult balance between their ecological precision and their ability to foster exchanges on a market for offsets.

Too much precision (i.e. the habitat for middle-aged great blue herons who don’t like shrimp of Robertson fame since 2004) might better reflect the complexities, or rather the ecological uniqueness, of each location (and time), being assessed. It would however make any market completely useless… At the other extreme, a metric that hardly encompasses these complexities (try wetland area) would make the market highly fungible.

This paradox should be on the mind of anyone developing metrics or methods for assessing ecological equivalence or credit-debit systems, or using them to actually design an offset scheme. The same applies to any type of ecosystem service market off course (PES or otherwise).

It is interesting to note that in their pilot schemes for testing habitat banking, France and the United Kingdom have made very different choices in terms of metrics. More on this later…