Why do we know so little about the ecology of tropical forests?
First of all because the number of tree species is nothing like the wealth of species found in temperate forests such as in Europe. Indeed in the tropical rainforest there are 1000 different species, of which one hundred are commercially viable. Of these, less than five account for 50% of exports to Europe and Asia. It is also because, over the last few decades, we have seen an erosion in scientific knowledge in the African countries in question, due to the under-funding of applied research and a lack of interest in forests on the part of backers. Result: the scientific community of the six main countries covered by dense rainforests (1) has few specialists in forest ecology and sylviculture. This is why the partnership with teams such as our Laboratory in Gembloux is important. In terms of research we're starting from scratch, or just about. So there is a severe shortage of basic data on the ecology of most tree species, including those that have been exploited a lot:  the Tali, the Okan, the Ayous, the Sepele and so on.  There is a lot we do not know about their natural regeneration, their genetic diversity, their demography, their need for light at different growth stages and so on.  Some species that are heavily exploited are fragile. The Ayous, for example, one of the white wood species that is much sought after in these forests, only bear fruit on average every eight years. It is therefore important to know more if we want to continue to exploit it in a sensible way. Species as common as the Iroko or the Tali have been studied very little in Central Africa. In certain cases, it would seem that even the basics need to be reviewed:  the name and taxonomic classification of certain species is dubious. It is only once we have this basic ecological data that we will be able to model the long-term development of natural forests.

For certain species it is sometimes interesting to push the genetic study quite far...
Yes, this is the case for the Tali, for example, a species which has great difficulty regenerating in the whole of Central Africa. Along with the ULB, in sites set up on the concessions of the companies Pallisco in Cameroon and Precious Woods in Gabon, we are studying the heritability of certain characteristics of this species - growth, configuration...- on trees from three different countries. An example of the kind of questions we are asking ourselves: if a tree is twisted will its descendants be twisted too? What is the provenance of the trees that is the most adapted to specific ecological conditions? The ultimate aim consists of obtaining trees with the most attractive provenance in terms of production, but also identifying those that develop the best capacities for resistance when faced with 'aggressive' outside agents such as significant climate change. Just over ten years ago this led us to create tree nurseries established on the sites of the logging companies that are the most advanced in sustainable logging, those that use FSC certification. There we can observe the development of young trees, particularly species that have more difficulty regenerating in the forest, and we test plantation programmes in tree fall gaps, skid trails and secondary forests. By 'secondary forests' we mean forestry sites which were once occupied by humans practising slash and burn agriculture. Now abandoned, some of them have been invaded by lianas, shrubs or species with short life-spans that are not very viable and do not safeguard the long-term survival of the forest. Of course we can consider this to be a 'normal' evolution of forests. But if so, let's not speak of 'virgin' forests. Most of all, let's not forget that if we leave such secondary forests be, they are far from being necessarily the richest in terms of biodiversity, nor those that can the most usefully perform the role of carbon storage to which the big tropical forests will necessarily contribute in the context of combating climate change.

What do we know about the past of these forests if they have not always been 'virgin' territories? Did these only become covered in forest in the last few thousand years? What did they look like before?
We have a pretty good understanding of the paleo-climatic phenomena that characterised these tropical areas. During the major glacial periods which took place every 100 000 years, these forests regularly lost a large part of their area, with some reduced areas then being turned into a haven for biodiversity. We also know that 2500 years ago, the forests of Central Africa were affected by a change in climate and greater seasonality. Moreover, these forests were largely occupied by man but there is a lot we do not know about the specific dynamics of this occupation. What were the population movements? How much ethnic mixing was there? Yet, this occupation probably played a significant part in the configuration of the forest right up until our time. If not, what is the explanation for the fact that most of the existing light-hungry species were able to establish despite substantial, fast-growing forest cover. This is why, in partnership with other disciplines (anthracology, archaeology, genetics, pedology…), we are studying and digging to look for charcoal and various debris as evidence of human activity. As the anatomical structure of wood is conserved during combustion, it is possible, using microscopic analysis, to get an idea of the vegetation present a few centuries ago and even to go back several thousand years. We can also gain a better understanding of the past climate in these regions by supplementing our anthracological work with contributions from dendrochronology (tree-ring dating) and palynology (the study of pollen).  Such digs, which are resolutely multidisciplinary and carried out in partnership with the Royal Museum for Central Africa in Tervuren and many other European partners, particularly as part of the CoForChange (2) project, are among the first of their kind in Central Africa. The interest of such researche, in a context of global change, has also been recognised by the FNRS (the Belgian National Funds for Scientific Research), which is funding one of our projects in Cameroon.

(1) The Congo Basin extends over the Democratic Republic of the Congo, Congo-Brazzaville, Gabon, Cameroon, the Central African Republic and Equatorial Guinea.
(2) The objective of CoForChange is to explain and predict possible changes in tropical forests of the Congo Basin:  it is about improving the effectiveness of public policy and programmes for the management/conservation of biodiversity conducted by African countries and Europe in this region. It is implemented by an interdisciplinary consortium directed by CIRAD (France); this consortium brings together eight institutions (including GxABT-ULg) of four European countries (Belgium, France, Italy and the United Kingdom), five institutions from four Central African countries (Cameroon, the Central African Republic, the Republic of Congo, and Gabon) and an international organisation. The project is funded by the ANR (France), the NERC (UK) and co-funded by the fourteen partners. It began in January 2009 and will last for 48 months.