This morning I followed Holger Thues (Curator of Lichens) to a remarkable place.

Not just any old trees ...

At first glance this short row of trees looks little more than a typical, beautiful countryside scene. However, these are elm trees and trees like these are a sight that has become exceptionally rare across Europe.

An increasingly rare sight in Britain and much of Europe, elm trees

Dutch elm disease has destroyed virtually all of the adult elm population in lower land Britain and much of Europe, and now many people only know elms from paintings and pictures.

The open canopy and twisted branches of elm trees

The elm has an open canopy and the trees bend and twist in a magical way that leaves a wonderfully spooky shadow. The Isles of Scilly are one of the last places you can see adult elms - the tree still survives on the mainland as a shrub, but as soon as it gets to a certain size the beetle which transmits dutch elm disease, can burrow into the bark and pass on the infection. Of course, Dutch elm disease has effected much more than just the elms themselves. These trees supported other life, including lichens and Holger showed me one of the rarer lichens that live on elm.

It isn't just the trees that are affected when they succumb to Dutch elm disease.

Tragically, this lichen also lives on ash and with ash dieback destroying so many trees, it has a bleak future. Holger described it as the ‘dodo of the lichen world’, forced into making bad decisions that ultimately could be it’s downfall.

Bacidia incompta (elm lichen), whose existence is linked to the under threat elms and ash trees

More optimistically, Holger found a very healthy population of a species that has declined dramatically over the last 100 years in the rest of the UK.

Heterodermia leucomela

This is a tropical lichen that now has the south west of Cornwall as it’s most northerly outpost. It is very rare in the rest of Britain but it seems the population here is doing very well.

Holger also showed me this photo of a specimen collected 100 years ago on Scilly - he was keen to find out if it was still here and if it was still so large! The size of the lichen is a sign of it’s vitality and it only occurs in a few local parts of the Uk and on Scilly.

Roccella fuciformis, collected 100 years ago on the Isles of Scilly

You can see it is still doing well on the islands.

Roccella fuciformis, still doing well on the Isles of Scilly

It goes to show how important collections are, specimens tell us so much much more than absence or presence. They tell us about the strength of a plant at a given time, what it looked like and how it was living and this means we can make judgments on it’s role in the ecosystem.

It really is a treat spending time with Holger; as a lichenologist he looks at the world in a completely different way to other scientists and the things that normally pass unnoticed become much larger and more interesting.

Holger sees the world in a different way

Although I have spent each day following different scientists, I think some of the most memorable moments have been in the evenings when the scientists come together, talk about what they have found and go through their specimens. I took this photo after dinner

The evening sort

The table is turned into a mess of equipment, specimens and reference books and exciting finds are shared amongst the group. It’s not possible to know everything about the natural world but it is possible to try and become friends with enough experts to give you a good idea!

By the way, if you would like to do some science of your own and help an important study, find out how to take part in the OPAL project's Tree Health Survey.