Wednesday, 21 March 2018

Garden plants: a threat to the environment due to climate change?

Last time Tomos Sion Jones appeared on these pages, he was telling us about an orchid course he was able to attend thanks to a BSBI Training grant

A year on and Tomos has started his PhD and now he wants to reach out to BSBI County Recorders. Over to Tomos: 

"Calling all BSBI Vice-County recorders (VCRs)! I’m a PhD student at the University of Reading, investigating the possible impacts of climate change on the distribution of garden plants and what threat garden plants present to the environment. Most garden plants are expected to have an increasing geographic range in the future. This could be a result of climate change. I’m interested in garden plants which have escaped ‘beyond the garden fence’. In particular, the factors influencing their transition along the introduction-naturalisation-invasion continuum (Richardson et al., 2000):
The introduction-naturalisation-invasion continuum. Red arrows show the transition processes and the black arrows represent the factors that influence the processes. Adapted from Levine et al. (2004:976) and Milbau and Stout (2008: 309).

Proportion of returned VCs 
(excl. the Channel Isles)
Data: OS data © Crown copyright
 and database right (2017)/
© OpenStreetMap contributors (2015).
"The initial element of this project is an online survey for BSBI VCRs. So far I’ve received completed surveys for 18 (of the 153) vice-counties across Britain and Ireland. The preliminary results from this survey are very interesting - especially on the ‘top five’ garden plants of increasing concern in each vice-county. That is, garden plants which are showing signs of naturalising or having invasive potential. Some of the results, such as Gunnera spp., are not a surprise. 

"However there are also results that I wasn’t expecting. For example, Narcissus spp., which are often naturalised but I wouldn’t have considered them to be of increasing concern. Also, Cyclamen hederifolium. It was introduced as early as 1597 (Stace and Crawley, 2015) and is a nice example of the ‘time-lag’ that’s often observed between introduction and naturalisation. C. hederifolium has certainly been naturalising recently but does it have invasive potential?

"It’s garden plants such as this that I’ll investigate further using ecological niche modelling. Comparing the climate of a plant’s native range with climate projections for Britain and Ireland will allow me to predict which garden plants might find future climate suitable and have an increased potential to naturalise or invade. 

Cyclamen hederifolium
Image: Meneerke Bloem / CC-BY-SA
"In the survey, VCRs are asked to rank their agreement or disagreement with the statement ‘climate change is exacerbating the impacts of garden plants on native plant species’. Interestingly, only five (27%) of respondents ‘agreed’ or ‘strongly agreed’ with the statement. This is much lower than I was expecting as I generally consider climate change as facilitating the transitioning process. However, it’s unexpected responses like this which are important for my project.

"I hope to receive completed surveys for as many vice-counties as possible so that I can compare the results for different parts of Britain and Ireland. So I encourage all VCRs to complete the survey. Many thanks to those who have already done so! If recording duties are shared for your vice-county, both/ all VCRs are welcome to complete it. If you would prefer to complete a hard-copy version, please email me with your postal address. You should read the information sheet before starting the survey. The survey will be open until Monday, 30th April [LM: this is an extension to the previous deadline]. If you have any questions, please email me.

"Please note that there’s an error which will affect VCRs for the Channel Isles. I’m afraid you’ll need to select vc112 Shetlands and leave a note on the survey explaining which of the Channel Isles you’re responsible for.

"I look forward to receiving more responses and sharing the results with the BSBI. I’ll have an exhibit at the next BSBI Exhibition Meeting and results might be used in published research".

Levine, J.M., Adler, P.B. and Yelenik, S.G., 2004. A meta-analysis of biotic resistance to exotic plant invasions. Ecology Letters, 7, pp.975-989.
Milbau, A. and Stout, J.C., 2008. Factors Associated with Alien Plants Transitioning from Casual, to Naturalized, to Invasive. Conservation Biology, 22(2), pp.308-317.
Richardson, D.M. and Pyšek, P., 2012. Naturalization of introduced plants: ecological drivers of biogeographical patterns. New Phytologist, 196, pp.383-396.
Stace and Crawley, 2015. Alien Plants. London: William Collins.