NI: Lightning in African tropical forests: from tree mortality to carbon dynamics

Lead Research Organisation: Manchester Metropolitan University
Department Name: School of Science and the Environment


Trees take in carbon from the atmosphere as they grow, but this is eventually released when they die. The sheer number of trees in tropical forests means that small changes in these rates of growth and death, and the resulting change in the balance of carbon taken in or released, can have a big effect on the climate. While a lot of research has focused on how changes in temperature and rainfall affects the growth and death of tropical forest trees, the potential effects of lightning have been largely neglected. A study tracking lightning strikes in Panama found that they caused more than half of all deaths of large trees, a previously undocumented effect despite being in one of the most intensively studied forests in the world. This project will provide important steps towards assessing whether this strong impact of lightning is a more widespread phenomenon.

Forests in Africa are characterised by a greater dominance of large trees than elsewhere in the tropics, so based on results from Panama they would be expected to be more vulnerable to lightning. Alternatively, the high frequency of lightning in Africa may have selected for trees that are better able to withstand its effects. Knowing whether or not lightning has a consistent effect across continents is important for determining whether future work should focus on understanding the causes of variation in the impact of lightning, or can instead explore the wider implications these effects.

The new international collaborator (Evan Gora) has developed an approach for detecting lightning damage from drone surveys and follow-up investigation on foot that allows large areas of forest to be surveyed. We will apply this at four sites along a dramatic gradient of lightning frequency in the Albertine Rift (on the boundary of the Democratic Republic of the Congo, Rwanda and Uganda) to (1) test whether trees at different sites in Africa are more or less vulnerable to being killed by lightning than those in Panama, (2) determine how forest structure varies with lightning frequency and (3) use these observations to assess the potential effect of lightning on carbon stocks and dynamics.

The project team will have regular online meetings throughout the project, will all meet in Rwanda to receive training from Gora in how to detect lightning damage, and a subset of the team will also meet in the UK after fieldwork. Collectively, these meetings provide considerable space to share ideas as the project develops, culminating in a five-year plan for future collaboration. We will seek wider input from scientist and stakeholders through a regular series of seminars and roundtable discussions, and will hold online training workshops to build capacity in monitoring the effects of lightning on tropical forests.


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Description The project aimed to determine whether the dramatic effects of lightning observed in the few neotropical sites where it has been studied are also seen in Africa, and whether these effects and associated risk factors differ within and between locations in Africa. Our first field campaign located over 40 lightning strikes (cf one strike that had previously been described in the scientific literature in Africa), revealing that diagnostic methods to detect lightning can be successfully used in Africa. Our results also indicate that lightning strikes appear to kill fewer trees in Africa than seen elsewhere, supporting the idea that forests which experience more frequent strikes are more resistant. We also found evidence that trees on ridges were more resistant to lightning than those in valleys. This indicates that lightning, and the ability of trees to survive it, could be an important control on tree species distributions in montane forests.
Exploitation Route Our methods for detecting lightning strikes have been employed by another team working in African forests (see collaborations section). Our results indicate a potentially important mechanism shaping species distributions, and better understanding of this will inform management of these forests (findings have been disseminated to protected area managers).
Sectors Environment

Description Findings have been disseminated to protected area managers, who are interested in whether increases in gaps in the forest represent a natural process or are a problem. We are in continued discussion with these protected area managers to explore the implications of our findings, and have shared all data collected with them.
First Year Of Impact 2022
Sector Environment
Impact Types Societal

Description PhD Bianca Zoletto 
Organisation Wageningen University & Research
Country Netherlands 
Sector Academic/University 
PI Contribution The idea for a PhD arose from discussions between the project team and Prof Sheil from WUR, who then developed a full proposal which was funded by WUR. The recruited PhD student (Bianca Zoletto) and an MSc student (Nicoloas Petridis) from WUR attended the first field campaign of our project in Nyungwe National Park and received training in identifying lightning strikes. They then used this training in their own fieldwork in Bwindi. Gora and Sullivan have continued to meet with Zoletto and Sheil as her PhD develops.
Collaborator Contribution Zoletto and Petridis joined the field campaign in Nyungwe National Park and assisted with data collection.
Impact Partners are involved in the preparation of a scientific paper from the first field campaign.
Start Year 2022