Are National Trust libraries at risk from climate change?

The National Trust delivered bad news for bibliophiles yesterday: its historic collection of around 230,000 books could become victim to the impacts of climate change.

Launching its 10-year strategy, National Trust leader Dame Helen Ghosh said that climate change is the biggest challenge faced by the conservation charity. In particular, she said, the rise in pests poses a threat to its libraries.

“Some of the bugs that we get in our furniture and in our books, for example silverfish, we used to only get those in the summer. They used to be killed off in winter. But because the winters have got warmer and wetter we get those kinds of bugs all year round,” she said.

Carbon Brief takes a look at what risks lie ahead for the National Trust’s literary collections.

Heating

Silverfish are tiny insects that are common library pests. They satisfy their carbohydrate and protein-heavy diet by feeding on paper, book covers and binding paste.

But these are not the only bug to cause nuisance in a library. According to Katy Lithgow, head conservator at the National Trust, furniture beetles, deathwatch beetles and clothes moths are also a concern for librarians, along with mould.

The National Trust collects data on the species and abundance of pests in its libraries, but the time scale is too short to be able to detect trends, says Lithgow, and certainly too short to be able to work out if potential trends correlate to climate change.

The assertion that the charity has already seen an increase in library pests is therefore largely anecdotal, says Lithgow, but in the sense that those working inside the houses are familiar with their history of insect problems. The number of insurance claims is also rising for the Trust’s properties, she says.

There are other studies that attempt to demonstrate the impact that increased warmth and damp could have on insects and pests, although the outcome varies depending on the species at hand.

For instance, a 2009 study by the Department for Environment, Food and Rural Affairs found that the clothes moth is among the nuisance species in the UK least likely to be impacted by climate change.

It also concludes that species that breed outside are more likely to be impacted by climate change than those that breed indoors, where temperatures are regulated for human comfort.

However, when it comes to National Trust and other historic buildings this is not always the case. In order to protect collections against potential damage from humidity, the temperature of the rooms is regulated to roughly follow the weather outside.

In wintertime, National Trust keeps its historic houses at an average of five degrees above outside temperatures, during which they are closed off to the public. A 2012 paper by Peter Brimblecombe from the University of East Anglia and Paul Lankester from English Heritage says:

“The increasing warmth expected for the climate of central England through the current century is likely to be propagated indoors and make interiors more favourable to insect pests. Despite the fact that the temperature increases are relatively modest (just a few degrees) the changes have the potential to alter insect lifecycles and numbers.”

This means that historic houses that are vulnerable to climate change may need more resources in the future to handle a potential increase in pests, the authors argue.

Leaky houses

The National Trust owns 140 libraries, which it says are “generally preserved in the places where they were originally assembled and read”, many of which are country houses.

This means that they are subject to the usual difficulties of maintaining the UK’s stately homes, including leaky roofs and walls.

According to its newly released strategy, the National Trust already spends a minimum of £100 million a year looking after its land and property, and will spend an additional £300 million over the next ten years just to clear a backlog of conservation work.

Ghosh blamed warmer winters for the proliferation of silverfish, but it is the increasing damp in these leaky buildings that is the main threat, says Lithgow. She tells Carbon Brief:

“We’re getting a lot more severe rainfall, and that finds its way into buildings through defective roofs, walls, drainage, ditches and stuff. As well as atmospheric moisture, all of those forces of moisture combined can sustain insect pests and mould much more.”

Attributing specific weather events to climate change is still an uncertain science. Yet scientists at the Met Office have already observed a slight increase in winter and decreased rainfall in summer over the last 250 years. This is in line with expected changes due to climate change.

In the south west of England, winter precipitation is predicted to be 23% higher in the 2080s, if the world continues on its current emissions pathway.

Lanhydrock, a Victorian country house in this region, is already suffering from mould due to a lot of rainfall. This country estate is only one room thick in many places, explains Lithgow, which makes it more susceptible to damp as the walls on both sides are exposed to the elements.

It will take more data collection before the National Trust can say for sure that its libraries are witnessing a climate-related rise in insects. But with a forecast for higher temperatures and increased winter rainfall, it is plausible that Britain’s leaky stately homes could witness a rise in unwelcome insect guests in the future.

Main image: Library.