Helping a humble mountain herb to beat the effects of climate change
The most pressing global challenge of our time is arguably climate change. Central to addressing this is the worldwideplantconservationundertaken by the Royal Botanic Garden Edinburgh (RBGE) and our partners.
From the Congolese forests, where monitoring of plant species underpins rainforest conservation, to Nepal, where the description of new species, coupled with economic and social botany, is helping communities benefit from sustainable plant resources, we are making a difference. But, if charity begins at home, what is RBGE doing for Scotland?
Scotland’s climate is projected to change. Already it appears warmer overall, with shifting patterns of rainfall. The challenge for Scotland’s plants is the added effect of climate change alongside other pressures.
This is exemplified by RBGE’S work on Cicerbita alpina, the alpine blue sow thistle, a tall herb characteristic of mountain grasslands. Highly palatable to grazing animals, it has become restricted to just four small mountain ledges in Scotland beyond the reach of deer and sheep.
Management of these animals connects directly with climate change, because smaller and isolated plant populations have lower amounts of genetic diversity, which reduces the ability of species to evolve and adapt to environmental change. New populations of alpine blue sow thistle, with increased genetic diversity, are being propagated at RBGE’S Nursery and translocated back into Scotland’s landscape. The key lesson is that local effects – such as grazing – can have implications for a species survival under climate change.
Aside from flowering plants, much of Scotland’s importance in international conservation stems from its richness of algae, mosses, liverworts and fungi, including lichens, which are archetypal in our landscapes, from the highest mountains to coastal rainforest.
What these humble species lack in stature, they make up for in importance; recent estimates suggest they capture around half of the nitrogen that later becomes available for plant growth and around 10 per cent of primary productivity overall. But, they are also microhabitat specialists and they occur under subtly contrasting conditions across the landscape.
Some species are associated only with patches of late-lying snow in the mountains and are threatened, therefore, by climate change. RBGE’S work includes discovering new spe- cies in these snowbed habitats so as to protect them before they disappear, with monitoring to understand the speed with which these habitats are changing. The challenge is to capture the importance of these high mountain areas within conservation policy at a time when they are shifting in character. This makes the practice of defining and then achieving conservation goals extremely difficult.
Perhaps the greatest test is reserved for coastal rainforest, part of a globally-rare temperate rainforest, covering less than one per cent of land surface in places such as Chile, New Zealand and, indeed, Scotland. Its very existence is sustained by particular climatic conditions; mild temperatures throughout the year, and plentiful moisture.
RBGE is using its three regional gardens as experimental sites to understand the response of rainforest species to climate change. Logan, in Dumfries and Galloway, is wet and warm while Benmore, in Argyll, is wet and cool and Dawyck, in the Borders, is dry and cool. As such, they provide sufficiently different
climates for monitoring the growth of rainforest lichens.
Lichen growth is measured monthly and compared to the climate. The variability of climates across the regional gardens is sufficient that we can estimate the effects of future climate change, including the potential health of lichen populations in Scotland’s rainforest over the com-
ing decades. Then, we can start to understand how we might manage our woodlands now and in the future.
Many of Scotland’s woodlands have been simplified because of past management such as coppicing for charcoal or oak bark to be used in tanneries. By increasing the complexity of these woodlands, such as diversifying the types, ages, and structures of
trees, we can create a wider variety of microclimates, giving lichens the opportunity to colonise and survive.
Our future wellbeing is intimately linked to the fate of plants and fungi. Climate change issues reach across land management options – grazing, woodland management and more – since local actions become part of our global response. Arguably, all conservation, from the eradication of invasive non-native species, to habitat restoration, is a part of the response to climate change. Each will seek to provide nature with as much resilience as possible and we can all play a part.
Dr Christopher Ellis is head of cryptogams, Royal Botanic Garden Edinburgh.