“The Botanical Garden’s appearance is going to change dramatically”

Some areas of the Botanical Gardens are even cordoned off at the moment…

Gallenmüller: This is for safety reasons: branches that have already died can snap and fall; we call this ‘sudden branch drop’.

What are the long-term consequences of the current situation?

Scherer-Lorenzen: The Botanical Garden’s appearance is going to change dramatically over the coming decades. We have developed a plan to tackle the garden’s redevelopment. Above all, this involves selecting different plant species. We must respond to the new climatic conditions – what happens in nature through natural processes, we are addressing here through horticultural means by considering which species are better adapted to drought. In the long term, the garden is likely to develop a more open, savannah-like landscape.

Many different plants of various origins grow in the Botanic Garden. Do they also differ in their responses to heat and drought stress?

Scherer-Lorenzen: Yes, they do. The Botanical Garden is like a laboratory where we can see how different species react. For example, we have a Mediterranean holm oak here that is thriving at the moment because it is adapted to dry conditions, although it is quite sensitive to frost. Particularly interesting for future garden design are species that originate from transitional zones between forest and steppe with a continental climate, and which are accustomed to cold winters as well as very hot, dry summers. The Turkish hazel from Asia Minor, for example, can develop mighty trunks even on barren, dry soils; the Lebanese cedar is also of interest in this context, as is the Turkey oak. Or certain beech species from warmer regions that are closely related to our native beeches. Our experiences naturally inform our garden design, but they could also assist in the selection of future urban trees, which are, after all, equally affected by this issue.

What can we learn about the consequences of climate change from all of this?

Gallenmüller: Our local regions contribute significantly to climate change, but until now the effects have tended to be felt elsewhere. Now, however, the consequences are beginning to be felt here too, and we are seeing and experiencing them ever more clearly.

Scherer-Lorenzen: In our ‘Future Forests’ Cluster of Excellence at the University of Freiburg, we are conducting research into what the forests in our regions will look like in the future and which tree species will characterise them. On sandy soils in the Upper Rhine Plain around Karlsruhe, for example, there are already areas where forest growth is no longer possible because it is simply too dry and too hot: Trees can no longer grow there; we already have savannah-like ecosystems in those areas. We are also investigating the molecular and physiological mechanisms that explain why one tree dies whilst another survives. Sometimes we even observe such differences within the same species in the same stand, which is incredibly fascinating. And the Botanical Garden serves as a kind of showcase for all these developments and our research into them.

What will the Botanical Garden need in the future?

Gallenmüller: As well as the long-term redesign of the garden, we need to completely overhaul the irrigation system; we require a much more efficient and sustainable system. The ideal solution would be an underground drip irrigation system, so that as little water as possible evaporates and the workload remains manageable. We have already been able to implement this in a few areas of the garden – thanks in part to donations from university alumni and members of the public. We are very grateful for this. The booster association ‘Friends of the Botanical Garden’ are also a great help to us.

Scherer-Lorenzen: To put it simply: climate adaptation is labour-intensive and costs a lot of money. Perhaps in future we’ll need something like crowdfunding for the garden…

Gallenmüller: Our garden is open every day and visitors can come free of charge. We also contribute to nature conservation and education; we welcome school groups and nursery classes here, organise events and guided tours, and provide information on topics such as nature conservation, sustainability and climate change. All of this is part of my favourite work, but it’s also very time-consuming.

Scherer-Lorenzen: What’s more, botanical gardens are, after all, a small but important part of global efforts to conserve biodiversity. Zoos are, of course, well known for their role in protecting endangered animal species. We want to do even more to protect endangered plant species here in our garden in future.