Post-2015 Consensus: Biodiversity Perspective, Brander
This perspective paper makes a proposal for improved methodologies for conducting large scale assessments of the costs and benefits of meeting targets for biodiversity and ecosystem change. This is driven by the recognition that currently applied approaches, such as those used by Markandya in the challenge paper, do not produce sufficiently accurate information for use in cost-benefit analysis. For example, the enormous span of results for the wetland program implies that we cannot estimate even the order of magnitude of benefits.
There are several related methodological problems. Firstly, values for ecosystem services are unlikely to be globally constant across an entire biome. Secondly, marginal values for ecosystem services are unlikely to remain constant as the stocks of ecosystems change. Thirdly, assessing this expected variation in values by using minimum and maximum values in a sensitivity analysis will produce an enormous range of results which are of little help in decision making.
To address these problems we propose to use meta-analytic value transfer methods combined with spatial data on biophysical and socio-economic determinants of ecosystem service values to produce spatially variable and more accurate estimates of benefits. We use this method to re-estimate the benefits of meeting the target on wetland loss.
In this analysis for wetlands, upper and lower bound values are calculated using 95% prediction intervals. Analytical results are given in table 1. In contrast to the cost-benefit analysis results presented in Markandya, the present analysis produces very different results and more clear-cut decision rules.
Table 1: Net benefits from Aichi Target 5: 50% reduction in rate of wetland loss
Markandya also raises the issue of uncertainty and questionable credibility of cost estimates from the CBD study, and we evaluate the target on coral reef protection to examine the effect of cost uncertainty. In this analysis, both costs and benefits are re-estimated using meta-analytic value functions. Results are shown in table 2. Our analysis showed both costs and benefits to be higher than those estimated by Markandya, but the overall outcome was much the same.
Table 2: Net benefits from Aichi Target 10: 50% reduction in rate of coral loss
Our analysis attempts to improve on the treatment of uncertainty in the value of ecosystem services. As such it only deals with the uncertainty arising from transferring values from primary valuation studies to out-of-sample policy sites. In addition it is necessary to systematically examine other sources of uncertainty (e.g. measurement errors in primary valuation estimates; biased sampling of available primary valuation studies; consistency and accuracy of spatial data on ecosystem type and extent) recognizing that this type of global analysis of costs and benefits of ecosystem change stacks multiple sources of uncertainty.