Wednesday, 9 May 2012

Mission: alien moth survey

How long? A minute. 
When? Anytime from mid June to late autumn.
How? Make observations and (1) enter records on the website, or (2) use the LeafWatch app for smartphones.
Why? Does the damage caused by the moth increase with the length of time that it has been present in a location?

Anecdotal evidence suggests that the amount of damage caused by  leaf miner increases over the first few years that the moth has been present in a locality. For example, many horse-chestnut trees in London are almost completely defoliated by early August, so it looks like autumn has come early, but currently in parts of south Devon, horse-chestnut trees only have a speckling of leaf mines by the middle of September.

Part of the aim of our science is to provide data to confirm anecdotes such as these, and to estimate precisely how quickly the levels of damage increase with the length of time that the moth has been present.

We have asked people since 2010 to score how much damage is being done to the horse-chestnut tree leaves. They can enter their location and date so that we can assess the damage. Since 2011 people can also get involved with the LeafWatch app. For those who have smartphones, this is a really convenient way of gathering records - each record is associated with a photograph (which helps us confirm

What do we do with the records?

Records of the moth's spread
Firstly, the distribution of many animals and plants in this country is recorded in 10 x 10km squares (based on the Ordnance Survey grid), and the horse-chestnut leaf-miner is no different. Forest Research have been collating the 10 x 10km square records of the horse-chestnut leaf-miner to monitor its spread. We pass on any confirmed records from new 10 x 10km squares to Forest Research to help with our understanding of its spread. (We confirm records with a photograph, which is either requested via the Conker Tree Science website for new squares, or is automatically included in the record from the LeafWatch app.)

Records of its damage
Secondly, we are assessing how the amount of damage to the leaves is affected by the length of time that the moth has been present. This is clearly shown on the LeafWatch app website.

We are also doing statistical analysis to confirm the observations, while taking account of the time of year (because the amount of damage increases throughout the year as the moths reproduce). The statistics we are using is a fairly complex method called ordinal regression.

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