How humble herbarium specimens hold the key to combating climate change

What can dried plants reveal about climate change?

With around seven million herbarium specimens here at Kew alone, each mounted leaf and flower holds a story, documenting the changing landscape of plant life across continents and through time. 

In the face of climate change, where understanding the impact on fragile ecosystems is paramount, these specimens act as botanical time capsules, providing us a glimpse into past climates. 

Scientists use the specimens to compare historical variations with present-day observations, unveiling the subtle and dramatic shifts climate change has brought upon plant populations. 

These comparisons act as a springboard for informed conservation decisions, allowing us to protect vulnerable species and safeguard the ecology that sustains life on our planet. 

Case in point  

Example 1: Tied together - Climate changes, flowering times shift 

Research by Calinger et al., gives us a perfect example of the kind of insights herbarium specimens can provide us in the context of climate change. 

The 2013 study in Ecology Letters revealed how such specimens uncovered a concerning trend: rising temperatures are shifting the timing of plant life. 

“Over the last decade, more than thirty studies have used herbarium specimens to analyse changes in flowering phenology over time” 

By analysing decades of specimens alongside historical temperature data, the study found that for every degree Celsius increase, plants in North America flowered an average of 2.4 days earlier! 

This seemingly small shift might not seem dramatic, but it has big implications. For example, a slight change in flowering times can clash with pollinator availability – meaning the plant’s flowers can’t be visited as the pollinator has yet to emerge – potentially throwing entire ecosystems out of sync. 

With this in mind, the message is clear: understanding these shifts is crucial to predict and mitigate the ecological disruptions brewing beneath the surface – and herbarium specimens are a key part of building that understanding. 

However, the story doesn't end there. Studying these specimens revealed geographic patterns in traits like height and flowering times, hinting at their potential responses to environmental shifts.  

Soil types and information on associated species gleaned from labels painted a vibrant picture of their surrounding ecology. 

This study is a powerful testament to the untapped potential of herbarium collections. In regions like Angola (that the study focused on), where traditional surveys are challenging, these dried specimens become invaluable sources of biodiversity information. 

Example 3: Old specimens, new solutions 

These specimens don’t exist just to be examined; they can also provide tangible solutions.  As detailed in a recent short film, herbarium specimens can be used to identify historically resilient plant populations that thrive in harsher, hotter climates. 

By studying certain wild plants, we can identify species with valuable traits such as drought tolerance. These traits can then be bred into our food crops through selective breeding, ensuring they continue to produce good yields even in drier conditions. 

Alternatively, crop relatives can be grown which are better adapted to the changing conditions. 

Here's the short, animated film featuring our Head of Collections Dr Alan Paton that illustrates this:  

This is just a glimpse into the vast potential of herbarium collections. However, unlocking their full power requires overcoming one major hurdle: accessibility. Currently, millions of specimens remain physically tucked away in cabinets, accessible only to those who visit Kew in person. 

Introducing our Digitisation Project 

Our ambitious Digitisation Project is combating this issue. We're digitising our entire collection of over 8 million dried plant and fungal specimens to make them freely available online to anyone with an internet connection. 

This unprecedented level of open access will allow researchers worldwide to tap into this immense wealth of data. Imagine, for example, a student in Brazil, studying the impact of drought on Amazonian rainforests, being able to analyse centuries-old herbarium specimens from the region – or anywhere in the world – all from the comfort of their home or laboratory. 

The potential benefits are manifold. Digitisation will accelerate the pace of research, fostering global collaboration and enabling scientists to ask new questions, identify previously unseen patterns, and discover hidden connections.