Life On Trees Programme

The ambition of the Life On Trees programme is to unveil the biodiversity intimately linked to key trees, as exhaustively as possible, using the latest technical advances for collecting and analysing samples. It focuses on tropical forests, which cover less than 7% of the world’s surface but constitute the largest reservoir of terrestrial biodiversity, probably more than 80% of which is still unknown. This ambitious objective has been made possible by the use of new techniques such as metagenomics and the creation of a dedicated team of scientists and professional tree climbers.

In addition to the new scientific scope, this programme presents itself, by means of emblematic and spectacular trees, as a privileged vectoŕ for communicating on the often little-understood theme of biodiversity and showing the tree for what it is: a splendid synthesis of the surrounding forest.

The tree is a symbol with a strong emotional impact. The idea of studying the life associated with a single tree is a simple concept that is immediately understood by everyone. It helps to explain how biodiversity is generated – the arrival of one organism on a tree creates favourable conditions for the establishment of a succession of others – and why the biodiversity of primary forests is particularly high – the tree offers a wide variety of microhabitats favourable to the establishment of species with different ecological requirements.

A complete investigation of the biodiversity of a tropical forest tree is an unprecedented undertaking. There is no data in the scientific literature on all the organisms living in a tree, from unicellular micro-organisms to vertebrates. With little or no previous reference, we have opted for a gradual, sequenced approach so as to make the necessary adjustments along the way. The exploration of a tree is therefore divided into several visits to overcome the problem of space (the tree can only accommodate a small group of people simultaneously), cover different seasons and adjust the time spent in the field if necessary.

The inventories carried out on three different trees in Peru and Colombia from 2021 to 2024 are the most exhaustive carried out to date but, like any biodiversity inventory in tropical forests, they cannot claim to have captured alĺ of the organisms that could host the programme’s study trees. A tree is a mini-ecosystem, by its very nature dynamic, continually exposed to new colonisations, which succeed or fail depending on a multitude of factors – the presence of food sources, favourable establishment sites, favourable microclimatic conditions – which also change during the course of the tree’s development. With the study being repeated at different seasons, and using a very large number of techniques, we can nevertheless consider that our objective of approaching the maximum value of eukaryotic biodiversity in our trees can be achieved.

Years will be spent studying the biological material collected. We can expect progress to be more or less rapid depending on the groups being considered, the volume of material to be processed and the availability of expertise. The partner and scientific coordinator of the Life On Trees programme, the Belgian Institute of Natural Sciences, is in charge of monitoring these analyses and feeding the programme database as the work progresses.

The initial figures already shed light on the extraordinary diversity of organisms that can be associated with a single tree, and demonstrate the value of deploying adequate human and technical resources to uncover it. There is no doubt that the trees studied are no exception and that such means, implemented elsewhere on other trees, would reveal similar situations. In other words, it is the biodiversity associated with large trees in general, particularly that of small organisms, that is certainly underestimated because it is poorly or inadequately documented.