Summary
[warning: this is my longest post ever...]
Nitin Sekar and I recently released a paper examining whether a large legal sale of ivory affected poaching rates of elephants around the world. Our analysis indicated that the sale very likely had the opposite effect from its original intent, with poaching rates globally increasing abruptly instead of declining. Understandably, the community of policy-engaged researchers and conservationists has received these findings with healthy skepticism, particularly since prior studies had failed to detect a signal from the one-time sale. While we have mostly received clarifying questions, the critique by Dr. Fiona Underwood and Dr. Robert Burn fundamentally questions our approach and analysis, in part because their own analysis of PIKE data yielded such different results.
Here, we address their main concerns. We begin by demonstrating that, contrary to our critics’ claims, the discontinuity in poaching rates from 2008 onwards (as measured by PIKE) is fairly visible in the raw data and made clearer using simple, valid statistical techniques—our main results are not derived from some convoluted “model output,” as suggested by Dr. Underwood and Dr. Burn (we developed an Excel spreadsheet replicating our main analysis for folks unfamiliar with statistical programming). We explain how our use of fixed effects accounts for ALL average differences between sites, both those differences for which we have data and those for which we are missing data, as well as for any potential biases from the uneven data reporting by sites—and we explain why this is better than approaches that attempt to guess what covariates were responsible for differences in poaching levels across different sites. We show that our findings are robust to the non-linear approaches recommended by Dr. Underwood and Dr. Burn (as we already had in large part in our original paper) and that similar discontinuities are not present for other poached species or Chinese demand for other precious materials (two falsification tests proposed by Underwood and Burn). We also show that previous analyses that failed to notice the discontinuity may have in part done so because they smoothed the PIKE data.
We then discuss Dr. Underwood and Dr. Burn’s concerns about our causal inference. While we are more sympathetic to their concerns here, we a) review the notable lengths to which we went to look for reasonable alternative hypotheses for the increase in poaching; b) examine some of Dr. Underwood and Dr. Burn’s specific alternative hypotheses; c) present an argument for inferring causality in this context; and d) document that trend analyses less complete than ours have been used by CITES to infer that the one-time sale had no effect on poaching in the past, suggesting that our paper presents at least as valuable a contribution to the policy process as these prior analyses. We then try to understand why the prior analysis of PIKE by Burn et al. 2011 failed to detect the discontinuity that we uncovered in our study.
Finally, we conclude by discussing how greater data and analysis transparency in conservation science would make resolving debates such as this one easier in the future. We also invite participation by researchers to a webinar where we will field further questions about this analysis, hopefully clarifying remaining concerns.
Overall, while our analysis is by no means the last word on how legal trade in ivory affects elephant poaching, we assert that our approach and analysis are valid, and that our transparency makes possible fully understanding of the strengths and limitations of our research.
