Extinction of Species .ORG

The Convention on International Trade in Endangered Species (CITES) bans international trade in species threatened with extinction. We investigate the effects of these bans on species’ endangerment, as assessed by the International Union for Conservation of Nature (IUCN). Our analysis exploits changes in CITES bans between 1979 and 2017. We find that CITES bans lead to subsequent improvements in mammalian species’ IUCN status, relative to species in which trade was not banned. These effects are primarily due to improvements in the status of commercially targeted species. On the other hand, CITES bans lead to deteriorations in reptilian species’ IUCN status. We find that major spikes in trade volume occurred in anticipation of the bans on reptilian species but not in anticipation of those on mammalian species.

More than 30,000 known species are currently threatened with extinction, and the resulting loss in biological diversity can have severe effects on ecosystems and on the value humans and other species derive from them.  Many species are threatened because dead specimens (or their parts) have a high value when traded in markets. To counter this threat, the 1975 Convention on International Trade in Endangered Species (CITES) treaty regulates international trade in certain animal and plant species. The highest level protection under the CITES treaty applies to species listed in Appendix I of the agreement, which CITES defines as “species threatened with extinction.” With limited exceptions, states that are party to CITES can neither export nor import, for commercial purposes, live or dead specimens of any species listed in Appendix I.

As a theoretical matter, trade restrictions can have positive and negative effects on species survival. First, trade can protect a species if it encourages sound resource management practices: Commercial fisheries are the textbook example of how the profit motive can aid in sustaining species populations. However, this conclusion does not extend to environments with incomplete property rights, resulting in the well-known “tragedy of the commons”, in which case trade restrictions may be needed to prevent unsustainable overharvesting. Second, bans on international trade do not restrict subnational trade. From the perspective of the supplying economy, an international trading ban is an export restriction that reduces domestic prices. Producers in the domestic market may respond to this price reduction not only by shifting to other more profitable economic activities (a substitution effect) but also by increasing the volume of harvests to compensate for lower prices per specimen (an income effect). The overall effect of international trade restrictions depends on the balance of these supply responses. Third, illegal export markets may partially or entirely replace previously legal trade, reducing the effectiveness of the trade ban. Fourth, producers that anticipate an impending trade ban may increase harvests while trade is still legal, counteracting the intended effect of the ban.

CITES Appendix II includes species “in which trade must be controlled in order to avoid utilization incompatible with their survival.” Commercial trade in these species is subject to regulations intended to ensure that transactions are not detrimental to the survival of the species and minimize the risk of injury or cruel treatment of the specimen. 

Findings: CITES international trade bans have been effective in promoting the survival of mammalian species.  

For reptilian species, on the other hand, the results are reversed: We find a statistically significant worsening effect of CITES trade bans. This worsening effect is generated by a shifting of probability mass from lower threat levels to higher threat levels on IUCN’s scale and is primarily driven by the effect of the trade ban on commercially targeted species. Therefore, the CITES trading bans appear to have hurt reptilian species and have hurt those species most that are targets of commercial trade.

Why has CITES been effective in protecting mammalian species but has had the opposite effect on reptilian species? An earlier study of the effect of CITES trade bans on trade volume found that imports of 46 animal species increased after the announcement of CITES trading bans but declined after the bans had become effective. Inspection of published CITES data on legal trade activity in Appendix I species confirms that a number of reptilian species in our dataset have seen sharp spikes in trade activity in the years leading up to a ban. Thus, one potential unintended effect of a CITES Appendix I listing is that it can spur a “last minute rush” in trade activity in anticipation of the trade ban. Could the harm caused by such rushes outweigh the bans’ benefits. Our results support this conjecture for reptilian species. On the other hand, the CITES trade data contain no evidence of trade spikes before bans in the trade of mammalian species, which can explain why the CITES bans have been effective for mammals.