This year’s UN Climate Change Conference (COP26) will be held in Glasgow in November, and now more than ever before, the pressure is on for world leaders to agree on climate action to keep global warming below 1.5°c. In the lead up to the conference, we’re asking our editors and authors to share their research at the interface of climate and ecology. In this post, Jesus Aguirre Gutierrez of the University of Oxford presents research on the role of functional diversity in the response of tropical forests to climate change.

Tropical forests are the most biodiversity-rich land ecosystems, hosting more than 50% of global biodiversity and responsible for more than 30% of terrestrial productivity, harbouring between 40,000 to 53,000 thousand tree species. These forests crucially contribute to people’s livelihoods in tropical regions (and beyond), which are home to ~40% of the world’s population, many of which are among the poorest communities in the world.

The impact of climate change on the tropics

Forests across tropical regions carry out pivotal functions such as resource uptake, cycling and biomass production and are crucial for terrestrial carbon sink dynamics. Given the wide distribution of tropical forest on earth, even small changes in the plant composition of such forests can have tremendous impacts on the removal of CO2 from the atmosphere and on other functions they carry out. Strikingly, recent studies suggest that the carbon sink in the Amazon tropical forest, the largest tropical forest in the world, is declining and that the African carbon sink is only stable, capturing 0.66 tonnes of carbon per hectare per year.

In the field we collect information about the characteristics of the plants across our forest sites. Such characteristics are related to the thickness, area, length, hydraulic conductivity and chemistry of leaves, and many others, but also about the colour and size of flowers.

What can the functional characteristics of plants tell us about forest resilience to climate change?

The services provision and functioning of tropical forests are tightly linked to the composition of morpho-anatomical, physiological and phenological functional traits of the species that compose them. We expect that greater stability of ecosystem functioning, such as carbon capture, may be obtained in regions that have a high functional diversity but also that have high redundancy of those trait characteristics. Despite their importance, we still lack knowledge on the distribution of plant functional traits, the functional diversity and functional redundancy of tropical forest ecosystems. Such knowledge is pivotal for biodiversity conservation, for understanding Nature’s contributions to people and arguably to understand tropical forests responses to a changing climate.

Here we are in a Natural Protected Area. We are examining the information we just collected using a handheld LiDAR (light detection and ranging) to obtain remotely sensed information of vegetation structure, and images collected with our drones and multispectral cameras.

Fieldwork in the tropics to sample their functional traits

To improve our understanding on the role of functional diversity for the response of tropical forests to climate change, I carry out field campaigns across tropical forest to census their vegetation and also to measure their traits such as leaf area, leaf thickness, wood density, levels of nitrogen and phosphorus in the leaf, hydraulic information and much more. Here at Oxford we have done this across several tropical forests including in Brazil, Peru, Ghana, Gabon, Malaysia and Australia. With all the information we have collected across the tropics about the plant species and their traits we can analyse how the climate may drive such distribution and how new climatic conditions may disrupt the observed distributional patterns.

How to track those responses with remote sensing

One big but exciting challenge is to extrapolate our findings from the plot level, usually with vegetation plots of 1ha, to the general tropics. For this I also use remote sensing with drones that have powerful multispectral cameras with which we built statistical models that relate the functional traits measured in the plot with their spectral reflectance. Based on these models at very high spatial and spectral resolution we are then able to take the next step and apply satellite remote sensing, using satellites, such as the Sentinel-2 from the European Space Agency. Using the Senitnel-2 satellites I am now working on pantropical trait maps of vegetation that can then be used to understand the effects of a changing climate on the distribution of biodiversity across the tropics.  

Although a bit difficult to get to the locations where we have set our vegetation plots it is always rewarding being in those beautiful natural areas and collecting such relevant information that will allow us to understand how forests around the world are responding to a changing climate.

Prospect for forest resilience and the COP26

During my research time I have learned that cooperation between people from different nations towards common goals is what makes magic happen. Without our partners in other countries I would not be able to do the research that I love, visiting different cultures and forests across the tropics. In the same way, if we really want to preserve biodiversity and keep our planet within the safe operating boundaries we need to thrive as society it is imperative we work together independently of our place of origin, culture and nation. COP26 in Glasgow is the ideal setting to share our dreams, our aspirations and most of all to work together for a diverse and inclusive future.

Jesus is an Independent Research Fellow funded by the Natural Environment Research Council and based at the Environmental Change Institute, School of Geography and the Environment, Oxford, UK. Read more about his work here.

Want to find out more about the upcoming climate conference? Read our handy Guide to COP26.