The potential impact of climate change on native plant diversity in Ireland
Volume 4 Number 2 - July 2007
Peter S. Wyse Jackson
Climate change has become a major issue of concern for governments and international agencies over the last few years as the realization has grown that climate change is becoming a reality, rather than what might have been perceived in the past as an ill considered ‘doomsday’ prediction by some scientists and environmentalists. With this growing concern, public opinion and understanding of climate change issues has heightened too. This is partly as a result of apparently increasingly unpredictable weather patterns in many parts of the world, which are attributed to climate change (although it is often unclear whether this is really always the case). While climate change is now seen as a reality that must be addressed as a common concern of humanity, there is, by and large, still seriously little concern for its impact on biodiversity in general and plants in particular.
In a foreword to Ireland’s National Climate Change Strategy 2007-2012 published this year, the Irish Prime Minister (Taoiseach), Bertie Ahern T.D., recognized that ‘Climate change is among the greatest challenges of our time’ (Government of Ireland, 2007). Nevertheless the Strategy itself pays little attention to the impact of climate change on Ireland’s biodiversity but instead concentrates on issues such as energy supplies, transport, industry, agriculture and waste – although it does acknowledge that “ecosystems are vulnerable to climate change with the risk of extinction for certain species, loss of tundra and certain forest areas”. In its section on Agriculture, Land-use and Forestry, the Irish Plan recognized that extensive planting of broad-leaved trees and hedgerows can help to contribute to carbon sequestration, but does not consider whether the species planted may themselves be impacted by climate change in the future.
At the international level specific proposals and actions are however now being considered to address the threats to biodiversity from climate change. For example, the UN Convention on Biological Diversity (CBD) at its forthcoming meeting of the Subsidiary Body on Scientific, Technical and Technological Advice (SBSTTA 12) in Paris in July 2007 will include climate change and biodiversity as an agenda item, supported by a discussion document prepared by the CBD’s Executive Secretary, that proposed the integration of climate change activities within the programmes of work of the Convention, including options for mutually supportive actions addressing climate change within each one of the Rio Conventions(CBD Secretariat, 2007a). In addition, the Millennium Ecosystem Assessment identified numerous links between biodiversity and climate change (Millennium Ecosystem Assessment, 2005). These initiatives recognized that to integrate biodiversity and climate change actions it will be necessary to:
a) Identify vulnerable regions, subregions and ecosystem types, including the components of biodiversity within these areas;
b) Assess the threats and likely impacts of climate change on biodiversity in the vulnerable areas identified;
c) Evaluate the climate change adaptation and mitigation options and measures proposed in relation to impacts on biodiversity, and
d) Implement and monitor the impact on biodiversity of adaptation and mitigation plans and measures adopted.
The CBD has also convened several meetings of an Ad Hoc Technical Expert Group on Biodiversity and Climate Change, which has developed a methodology to evaluate the risks to biodiversity from climate change, results of which are included in the CBD Technical Series No. 25. The CBD has also prepared a further important document in relation to climate change and biodiversity which include abstracts of important case studies contributed by experts worldwide, to support the SBSTTA meeting in Paris in July 2007 (CBD Secretariat, 2007b). In that publication the United Nations Secretary General, Ban Ki-Moon, noted that it is appropriate that the 2007 International Biological Diversity Day should focus on “Biodiversity and Climate Change” as integrating the mutual concerns of both will be fundamental to the achievement of the Millennium Development Goals.
Despite the above developments, the specific issue of climate change and plant conservation has been little considered to date. However, The Gran Canary Declaration II on Climate Change and Plant Conservation is an important new awareness-raising exercise and call to action, drawing new attention to the urgency of addressing plant loss as a result of climate change (BGCI & Cabildo de Gran Canaria, 2006). The Gran Canaria Declaration II also provides a useful list of taxa that may be most significantly impacted by climate change:
- Taxa with nowhere to go, such as mountain tops, low-lying islands, high latitudes and edges of continents;
- Plants with restricted ranges such as rare and endemic species;
- Taxa with poor dispersal capacity and/or long generation times;
- Species that are susceptible to extreme conditions such as flood or drought;
- Plants with extreme habitat/niche specialisation such as narrow tolerance to climate-sensitive variables;
- Taxa with co-evolved or synchronous relationships with other species;
- Species with inflexible physiological responses to climate variables;
- Keystone taxa important in primary production or ecosystem processes and function; and
- Taxa with direct value for humans or with potential for future use.
Internationally, significant efforts are continuing to improve and refine the quality of global and regional climate change models. The Irish Climate Change Strategy says that sustained efforts will be required in Ireland to maintain and develop climate modeling and down scaling capacity in order to ensure that these improvements inform decision-making at national and local levels. To date in Ireland there have not been significant high-resolution studies undertaken to measure the potential impact of climate change on plant diversity, applying the climate change models in a quantitative way to review likely changes in the Irish flora and ecosystems.
Predicted changes in Ireland’s climate as a result of climate change include:
- Rises in the mean annual temperatures: between 1890 and 2004 mean annual temperatures in Ireland rose by over 0.7°C and six of the ten warmest years during this period have occurred since 1995. Predicted scenarios suggest that by 2050 there will be an increase of January temperatures of 1.5°C in Ireland and July temperatures of 2.5°C.
- Changes in rainfall and precipitation patterns: a marked reduction of between 25% and 40% in summer rainfall is also possible, according to predictions, as well as perhaps some winter rainfall increases.
- More frequent storms: The frequency of severe storms coming to Ireland from the Atlantic Ocean may increase by about 15%.
- Increase in extreme weather events: such as floods, droughts, heat waves etc.
In 2005, work began in Ireland to develop and subsequently to implement a National Plant Conservation Strategy (National Botanic Gardens, Ireland, 2007). This Strategy proposed a set of targets, actions, milestones and indicators for Ireland to fulfill its obligations under the Global Strategy for Plant Conservation (GSPC) as part of its commitments to the CBD (CBD Secretariat, 2003).
In order to contribute towards this National Strategy, this author undertook a preliminary qualitative assessment of the possible impact of climate change on the native Irish flora, with the aim of obtaining a clearer view of the possible (or even likely changes) in the Irish flora composition over the next c.50 years and to help inform conservation priorities and measures needed for plant diversity conservation in Ireland. A total of 850 native plant species were assessed in relation to the list of criteria for Climate Change-vulnerable taxa given in the Gran Canaria Declaration II (above) and the predicted changes in the Irish climate. The results of this assessment are given below. It is stressed however that this is a ‘qualitative’ assessment only and the results should be regarded as very preliminary. It is urgent therefore that an experimental approach to the assessment of climate change vulnerable taxa is applied in Ireland and elsewhere in order to develop predictive models for specific plants and groups of plants. Such models can then be used to support and inform better decision-making and to guide the plant conservation measures undertaken. The potential role of botanic gardens in undertaking such research studies should also be stressed, utilizing their ex situ collections and wide ranging facilities for scientific study, as well as for plant cultivation, propagation and long-term monitoring.
The situation in Ireland
It is suggested that the plant species that will be most heavily impacted by climate change in Ireland are the following:
- Species that are already threatened in Ireland due to a variety of factors and reasons
- Species that occur in restricted or vulnerable habitats (such as ‘alpine’ type habitats in the mountains, coastal sites, peatlands and other wetlands, wetland margins etc).
- Species that are particularly prone to loss due to competition from invasive alien plants.
- Species that may be adversely affected by related changes to the biodiversity in their ecosystems as a result of climate change (such as loss of pollinators, seed dispersal agents etc).
The spread of new pathogens, such as new insect pests, vectors and diseases, may also be an increasing consequence of climate change and have an impact on native plant diversity. However, the prediction of what will be the result of these on specific plant species is difficult to predict and has not been included in this assessment.
Using these criteria an assessment has been made as to whether each native species (vascular plants only) in the Irish flora is likely to be impacted by climate change in a detrimental way or not. The impacts on specific species are not listed here and only a summary of the overall results of the study are provided. A list of threatened plants in Ireland provided on the website of the National Botanic Gardens (www.botanicgardens.ie) was used for reference to review whether already rare or endangered native plants would be further threatened by climate change. No species is currently included in this list on the basis that it is threatened by climate change. Eleven species (1%) of the Irish native flora are currently either ‘extinct’ or ‘extinct in the wild’.
The assessments revealed that, conservatively, there are at least 171 native plant species (20% of the total native flora) that appear to be particularly vulnerable to climate change during the period 2007 to 2050. Of a total of 143 threatened species currently included in the Irish threatened plants list, 74 species (52%) may have their situation made potentially worse due to climate change. In addition, 28 (3%) species that are currently not threatened in Ireland are likely to become so due to climate change.
It is also likely that plants of woodlands, long-lived species (such as trees) and species that are abundant in Ireland are generally less likely to be threatened by climate change, at least not by 2050. Species that occur in widespread and stable habitats may also be only marginally affected, such as those of hedgerows and grasslands. Species that occur in habitats that are already subject to periodic drought and / or inundation may also be relatively adaptable and resistant to climate change, such as submerged aquatics, species from dry walls and well drained rocky places.
Nevertheless there is a wide range of species that are potentially vulnerable to the predicted Irish climate changes and unless specific conservation measures are put in place, both in situ and ex situ, it is likely that Ireland could lose a significant proportion of its native plants as a result of climate change. The question has to be asked in relation to these findings – in what ways must the focus of the plant conservation plans and programme of the National Botanic Gardens of Ireland be changed or adapted to respond to an increasingly serious plant conservation challenge? A programme to address national targets for the GSPC has already been developed (and through them, to contribute to the relevant international targets). That includes ensuring that by 2010 the Gardens are involved in or contributing to the development and implementation of a range of species conservation and recovery programmes. Our institutional target includes the inclusion of all critically endangered plants in an ex situ conservation programme, with the addition of 3 to 4 other species each year. The institution is also involved in several existing and proposed All Ireland Species Action Plans for endangered species, such as for the orchid Spiranthes romanzoffiana and the Killarney Fern, Trichomanes speciosum, both of which are protected in Ireland under the European Union’s Habitats Directive (Europa, 2007). The institution expects to be increasingly involved in such programmes in the future and climate change impacts may result in more species becoming priorities. However, be that as it may, the existing critically endangered species will probably still remain as the most urgent priorities for action. Further initiatives that will also need to be developed include specific measures and continued vigilance in relation to existing and potentially invasive species (plants and animals), pests and diseases, so that increased pressure on already hard-pressed natural and semi-natural ecosystems and the species they contain can be managed, hopefully more effectively. The responsibility to help conserve, monitor and raise awareness of these threats to native plants and their habitats from climate change is a considerable challenge for botanic gardens in Ireland, as indeed it is for botanic gardens worldwide. Our efforts to conserve endangered plants ex situ, as a back up to in situ measures, are made even more valid and necessary as a result of climate change, when natural habitats for many threatened plants may no longer be able to support their indigenous species.
- BGCI & Cabildo de Gran Canaria, 2006. The Gran Canary Declaration II on Climate Change and Plant Conservation. BGCI, London, UK & Cabildo de Gran Canaria, Las Palmas de Gran Canaria, Spain.
- CBD Secretariat, 2003. Global Strategy for Plant Conservation. CBD Secretariat, Montreal, Canada. http://www.cbd.int/programmes/cross-cutting/plant/default.asp accessed 4th July, 2007.
- CBD Secretariat, 2006. Guidance for promoting synergy among activities addressing biological diversity, desertification, land degradation and climate change. Technical Series No. 25. CBD Secretariat, Montreal, Canada. http://www.cbd.int/doc/publications/cbd-ts-25.pdf
- CBD Secretariat, 2007a. Proposals for the Integration of Climate Change Activities within the Programmes of Work of the Convention. UNEP/CBD/SBSTTA/12/7. CBD Secretariat, Montreal, Canada http://www.cbd.int/doc/meeting.aspx?mtg=SBSTTA-12 accessed 4th July, 2007.
- CBD Secretariat, 2007b. Emerging Issues for Biodiversity Conservation in a Changing Climate. Technical Series No. 29. CBD Secretariat, Montreal, Canada http://www.cbd.int/doc/publications/cbd-ts-29.pdf
- Europa, 2007. Habitats Directive (92/43/EEC) http://ec.europa.eu/environment/nature/nature_conservation/eu_nature_legislation/habitats_directive/index_en.htm
- Government of Ireland, 2007. Ireland National Climate Change Strategy 2007 – 2012. Department of Environment, Heritage and Local Government, Ireland.
- Millennium Ecosystem Assessment, 2005. Millennium Ecosystem Assessment: Ecosystems and Human Well-being – Biodiversity Synthesis. World Resources Institute, Washington, USA.
- National Botanic Gardens, Ireland, 2007. A National Plant Conservation Strategy for Ireland (Final Draft). National Botanic Gardens, Glasnevin, Ireland. http://www.botanicgardens.ie/gspc/inspc.htm accessed 7th July, 2007.
Peter S. Wyse Jackson
Director, National Botanic Gardens of Ireland
Glasnevin, Dublin 9. Ireland