A Habitat Suitability Index is a walkover survey for great crested newts (Triturus cristatus). It is a probabilistic assessment, since it is the habitat quality that is being assessed, not the physical presence of the newts themselves. Because it is the habitat that is appraised by our ecologists, and that changes very little in a single year under normal conditions, this type of survey can be done at almost any time of the year.
The cliff notes are that your site will be classified as either poor, excellent or somewhere in between. Anything classified as ‘average’ or better will trigger phase 2 great crested newt surveys. Anything classified as below average or poor will not, suggesting instead that the risk of harm to newts at your site, arising from your development plans, is acceptably low – so as to be considered insignificant. (…Unlike the site below, visited by our surveyor Craig Williams in March of 2014.)
How We Work
Being the customer-centric company that we are, we like to be sure you actually need a great crested newt survey before we even start talking price and timescales. We do this by opening a simple conversation with you, to garner a few key pieces of information about your site that enable us to make an informed recommendation. Normally we’ll ask you for a site plan, and ask you to describe the site in your own words, as well as making use of aerial photography. Of course, it is true that many of you reading this will have already been told by your local planning authority that you need a great crested newt survey to validate your application. That being the case, we can have this sorted for you in a jiffy. All of our ecological consultants are capable of undertaking Habitat Suitability surveys for our amphibious friends and many of us have European protected species licences to assist with newt translocation and mitigation.
Originally designed by Oldham, et al. (2000), a HSI newt survey involves assessing your site against a set of 10 different habitat criteria that scores values between 0.01 and 1.00. These values are multiplied together and raised to the power 0.1, to produce an index score (a ‘geometric mean’ in geek-speak). The calculations above do not allow for your HSI score to be exactly zero, since the lowest score in any one of the 10 categories assessed is 0.01, as otherwise it would imply that the ecologist knows to a certainty that great crested newts are not present, which however likely, clearly isn’t true in the strictest sense.
However, equally, it is not possible to simply design mitigation (and skip a step) just because the HSI for the site grades the habitat as ‘excellent’. Essentially, the HSI is a useful scoping tool that in the majority of instances can eliminate the need for phase 2 surveys at your site. In the reverse scenario, where your habitat is graded as average or better, you will not be able to progress your planning application without the benefit of and accompanying report of full ‘phase 2’ great crested newt surveys – seasonally limited from mid-March to mid-June.
The Future of Testing
However, in the future it might be possible to determine the presence or absence of great crested newts, by simply taking a sample of the water and sending it off for eDNA analysis, which will dramatically reduce the time it takes to produce your survey and report, to say nothing of probably halving the costs, and within reason, this could be done at any time of the year!
Oldham R.S., Keeble J., Swan M.J.S. & Jeffcote M. (2000). Evaluating the suitability of habitat for the Great Crested Newt (Triturus cristatus). Herpetological Journal 10(4), 143-155.