A solution to monitoring of small populations

It is common for a company to be required to monitor certain species that may affected by their operations or for governments to introduce management measures for protection of rare or endangered species. You would be hard pressed to find anyone who seriously objects to this; it is a reasonable requirement for protection of the environment to monitor whether an activity that may be adversely affecting a protected species and to introduce measures for their protection.

For rare or endangered species, the monitoring program should be designed so that changes in abundance can be reliably detected. Companies and government often commit a large amount of money and resources to managing rare and endangered species and it is critical to know if these measures are being successful and the population is growing. It is also critical to know if the measures are unsuccessful and the population is continuing to decline. Also, because of their rarity, these changes, either positive or negative, must be detected in a relatively short period of time so that responsive management measures can be applied if necessary for protection of the species.

I have previously written about the problem faced by small populations; ‘…small populations are much more likely to go extinct that large ones’ . Unfortunately it only takes a cursory look at monitoring programs put forward by companies and government to realise that very little thought is given to the getting the monitoring right. For example a review by Taylor et al (2007) published in the journal Marine Mammal Science found that 72% of whale monitoring programs, 78% of dolphin/porpoise monitoring and 55% of polar bear monitoring programs conducted by the US government did not have the power to detect a 50% decline in abundance over a 15 year period.

Monitoring trends in abundance of very rare or endangered populations is particularly difficult because the monitoring method cannot be any more precise than the variance in population size. There is an unfortunate tendency when it comes to the monitoring of ‘charismatic fauna’ populations to focus more on the ‘greenwash’ and photo opportunities than on management. It doesn’t have to be this way; with some thoughtful planning it is possible to obtain hard data that can provide basis for responsive environmental management.

There are several population viability models available that can be used to estimate the risk, measured as probability, of a species going extinct over a given time frame (examples that I have used are Vortex and RAMAS). So if you are able to define the accepted level of risk, for example 50% over 15 years, it is possible to carry out an analysis of the population viability to determine the critical population number. The goal of the monitoring program then becomes to, at the minimum, allow detection of population trends that may lead to the critical population number being reached. Iterations of different survey design options, coupled with statistical power analysis, can then be used to develop the optimum monitoring program. It is not rocket science, nor necessarily more expensive than the business as usual case, so let’s do it.

 

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