HortWeek Podcast

In the hot summer of 2022, RBG Kew lost more than 400 trees. By July 2024, Kew announced that it believed over 50% of its trees could be at risk by 2090 due to environmental changes due to climate change.

This week's guest is Kevin Martin, head of tree collections at Royal Botanic Gardens Kew and he joined the HortWeek Podcast to relate the research Kew has done that led it to such a stark conclusion.

"What we started to look at first was mortality data, but we soon realized that that's a really unstable data set. can't always know why a tree or a plant has died in the landscape. It's not always due to environmental factors.

"We then started looking at climate modeling...and using species observation data to start building a better picture of the impact of climate change on the living landscape here at Kew.

Perhaps surprisingly, the focus was not on identifying vulnerable species, but "the provenance of the seed".

Kew studied its own environment, located as it is in "an urban heat island" on the edge of Greater London with relatively thin and poor soil, "so the effect of climate change is always exaggerated". 

To understand the plants that suited this environment, they found themselves in the Romanian steppe which proved a good match.

His next trip will take him to Georgia to find more species that might thrive at Kew.

Rather than building more and more glasshouses to create the right condition for plant collections, with their huge energy bills, botanic gardens must play to their strengths and grow the plants that fit their ecosystem and climate profile.

"And the native, the English native one is a really interesting question. 

"You've got Quercus robur, they all have a large distribution range. So we're now looking at their dryest range to understand how those trees have adapted...they will grow right up to the edge of Azerbaijan, right on the dryest edge of their range. So we're selecting seed from those areas to bring them back to Kew to understand how they've adapted."

And the change needs to translate to all green spaces and gardens, large and public as well as domestic and small.

"A lot of the plants that we all go to the garden centre to put in our own private gardens, those trees have been selected for us realistically by the Victorians. A lot of those plants are available in commercial nurseries, they're all from the original plant collectors from the Victorian era especially, and they're the same cloned material that's just passed round.

"So it's really not just changing the planting palette within Botanic Gardens...This is a change of planting palette... and that does need support and investment in further research from government in order to support the commercial nurseries as well.

"I do think it's going to be the biggest shift we've seen since the start of the organisation back in the 1840s". 

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