Actual and potential effects in complex ecological systems

In the government's RMA announcements last week, the part "narrow the scope of the resource management system to focus on managing actual effects on the environment" set off my ecologist spidey senses.

Potential effects are fundamental in ecological assessments, because we will never have a perfect understanding of ecological systems.

One important factor in our imperfect understanding (and there are many others, but this is a pretty common one), is that there are constraints on how and when we can conduct surveys to understand the ecology of a particular site. For example, you don't want to survey for long-tailed bats in winter, because they are less active and you're less likely to pick up their calls. Similarly, winter is usually a bad time to survey for fish and macroinvertebrates in rivers, because higher flows can affect what is there as well as your ability to conduct surveys.

A consequence of this is that often, resource consent applicants won't have the kind of thorough ecological survey information available to determine what species live there. We need that kind of information to determine the actual effects of a proposal. If we don't have a good understanding of the species that are present, consent conditions might include management plans to cover the potential species that might be there. An alternative would be to send the applicant back to collect more information so that the actual effects can be better quantified.

Freshwater ecology is full of probabilities and potential effects because of the complexities of these systems. I might not be able to predict with 100% certainty that a wastewater treatment plant discharge will cause significant deoxygenation in a river, for example, but if a discharge happens at the same time as, say, an especially hot day with low flows, the probability of significant adverse effects is much higher, and we might end up with dead fish on the river bank.

With all that in mind, I am wondering if there might be unintended consequences of focusing on "actual effects"?

Disclaimer: not advice, just my thoughts and opinions.

Sources and further reading

• Quality Planning: The Quality Planning Resource

• Environment Guide

• Beehive announcement: Replacement for the Resource Management Act takes shape