The United Nations conference on climate change which is due to take place in Paris at the end of 2015, is likely to add urgency to the reforestation programmes agreed upon by the international community. Planting trees favors carbon fixation through the process of photosynthesis. However, scientists are concerned about a too-hasty implementation of these strategies and are sounding the alarm. They consider that too little is known today about tropical grassy ecosystems such as savannahs, cerrados, meadowlands, lawns or open forests, to justify proceeding with such a massive undertaking without first carrying out detailed regional analyses. The researchers at Gembloux Agro-Bio Tech (of the University of Liege) warn that biodiversity could be seriously damaged due to a lack of knowledge about these habitats. These ‘old growth grassy biomes’ as they are known, harbor an exceptional biodiversity which is unique in the world and uncontrolled reforestation programmes could lead to irreparable biological losses.

According to the World Resources Institute (WRI), an American think tank active in the area of research, there are some 23 million hectares suitable for environmental reforestation which represents an area twice the size of the entire continent of South America. Good news for the environment? In principle the answer is yes because such programmes would make it possible both to address climate change (the vegetation resulting from such an initiative would allow for the progressive fixation of carbon through photosynthesis) and to make progress towards achieving what is known as the ‘Bonn Challenge’. In September 2011, the international community decided to commit to a gigantic project involving the restoration of 150 million hectares damaged by deforestation or other forms of degradation of soils and ecosystems.

But there is a major concern. The map used by WRI for compiling estimates which appeared in the journal Science in 2014 is too general and could lead to confusion among reforestation managers. An even worse scenario is that this could lead to counter-productive decisions both in relation to the fight against climate change and also with regard to the protection of biodiversity. This is the opinion held by a group of scientists from some ten European and North and South American universities including the Biodiversity and Landscape Unit of the University of Liege

The Katanga experiment

All these universities are united by a shared knowledge of these tropical grassy ecosystems. Gembloux Agro-Bio Tech, for example, has a wealth of knowledge concerning the study of natural outcrops in Katanga (in the Democratic Republic of Congo) that are rich in copper and cobalt. These involve mining environments that are rare on a world scale and which are colonized by very particular plant communities. This expertise enables scientists from Gembloux to advise the local authorities and mining companies on the implementation of programmes aimed at limiting the inevitable damage caused by mineral exploitation and where possible, to restore the damaged ecosystems.

While the greater public may see the African Savannah as the typical example of this type of grassy ecosystem, these systems are in fact much more varied than the idealized image, point out Grégory Mahy and Soizig LeStradic, one of whom is a Professor and the other a researcher at the Biodiversity and Landscape Unit, and who, along with their international colleagues, are signatories to the recent letter of caution published in Science (1), in response to the map published by the WRI. Among the many types of extremely polymorphic grassy ecosystems to be found across the globe are Cerrados or Pampas in South America, Savannahs in Africa, Prairies in North America, Calcareous grasslands in Europe and also tropical open woodlands. “The diversity of these natural environments is very important. It ranges from lawns to places where the vegetation is only a few centimeters high and where no tree can anchor itself, to open woodlands (like the dry tropical forests), to prairies or savannahs where the grassy vegetation can reach 1.5 to 2 meters in height”.

(1) Tyranny of Trees in Global Climate Change Mitigation, Science, 347, 2015