Thursday, 6 October 2016

Why record common species?

We heard on the radio today that the 'Common Toad' was in serious trouble. Sadly, its name suggests that it is still common, and yet the evidence points in quite a different direction. My experience in Mitcham strongly points that way. When my team surveyed the common in 1984 we did regular assessments of the breeding population of both frogs and toads. There were literally thousands of toads that spring. Sadly, a major fire some 500 metres from the main breeding pond killed a substantial part of the toad population that autumn. Crows had a magnificent feast for a long while afterwards!

Toads continued to breed in the ponds for several years but numbers declined; both within the main pond whose population had been catastrophically damaged, and elsewhere. Regrettably, nobody did regular counts in subsequent years so the impact of the fire is difficult to assess. Was this event the start of the decline or did something else happen? I cannot help feeling that the introduction of common carp and the destruction of weed beds in the ponds played an important part in the Toad's decline, but maybe there were other factors too?

The loss of such a thriving population is a tragedy but it has wider implications. I recall that in the late 1970s and early 1980s I occasionally happened across dead toads with infestations of the Calliphorid Lucilia bufonivora. That too is regarded as 'common' but I rather suspect that is no longer the case (NBN data seem to indicate a contraction but I cannot be sure). Had we had the levels of biological recording that we have today back in the 1970s, perhaps we could say a lot more about the decline of the 'Common Toad' and what has happened to Lucilia bufonivora.

This sorry tale has numerous parallels, such as the demise of the Passenger Pigeon - a once abundant bird in North America that is now extinct!

So, moving on to today's world in which there is increasing capacity to maintain all records, why don't we record common species more consistently? Only this morning a a major contributor to the Hoverfly Recording Scheme commented to me that he was unsure how much I would value repeated records of commoner hoverflies. My answer - to the contrary, we are keen to get good date runs of records. This is one reason why I now make an effort to log everything I see when out on my daily walk. Daily fluctuations are an important body of information that can be stored quite easily but cannot be reconstructed once the time has passed. We just don't know what our data might be used for in the future so the wise course is to log what one sees.

In a broader context, Brexit poses quite a serious risk to our wildlife. We really need to be on top of the issue and able to detect any changes that result from the loss of agri-environment schemes and intensification of farming practices. Making sure we record common species is an important first step - if we don't record common species we may not pick up problems in the countryside until the effects are extreme and even more difficult to reverse.

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