The Nicaraguan government is reviewing an environmental and social impact study for a proposed 300-kilometre canal to connect the Pacific and Atlantic oceans. As members of the specialist team who contributed to the 'baseline' biodiversity assessment for the study, we are in a position to respond to critics of the proposal (see, for example, A. Meyer and J. A. Huete-Pérez Nature 506, 287–289; 2014).

The internationally recognized environmental consulting firm ERM was commissioned to produce the study. Our impression is that ERM's dealings with its local counterparts, the Nicaraguan government and the company that owns the canal concession have been mutually transparent and professional.

Contrary to the depiction of the proposed canal route by Meyer and Huete-Pérez as a pristine wilderness, human impacts are strongly evident over its entire length, particularly from agriculture. This includes nationally and internationally protected areas and Lake Nicaragua, where several fish species are already in decline (T. B. Thorson Fisheries 7, 2–10; 1982; and M. T. McDavitt Shark News 14, 5; 2002).

We share many of the authors' concerns for environmental integrity and biodiversity along the proposed canal route. However, there were huge losses to these even before the canal project began, and this needs to be factored into the discussion.