Le site de vulgarisation scientifique de l’Université de Liège. ULg, Université de Liège

Thank you gorillas!
1/26/16

Open canopy, a sign of success

canopeeShould we be grateful to the gorillas? It would seem natural to think so because without the existence of these and other animals and their contribution to the effective dispersal of seeds fertilized by their fecal matter (thereby supplying minerals and humidity), these seeds would have less chance of developing into healthy and vigorous plants and therefore into plants that can be beneficial for humans as well. Another observation corroborates this assessment: the seedlings develop much better under an open canopy than in the forest where the light cannot penetrate. “The positive effect of dropping seeds in open habitats has already been mentioned, but this is the first time that the role of light has been directly demonstrated. In order to quantify this, I used hemispherical photographs of the canopy (at 360°C) taken vertically from the ground. Using softwares, I was able to transform the pictures into contrasting black and white images revealing the percentage of the canopy that was open. It emerged that the canopy around the gorilla nest sites showed a 7% to 10% level of openness. Apart from these sites, where the canopy was closed, the level of openness was only around 2% or 3%. The difference may not seem much but it is a determining factor: the seedlings develop two to ten times more rapidly in the open sites. Luminosity in tropical forests is a fundamentally important factor”.

The gorillas therefore drop the ingested seeds where these have a better chance of developing: in the light. They are effective agents of directed seed dispersal. This discovery is of fundamental importance: it seems to show that the western lowland gorilla populations, which are resilient to forest expoitation as it is often practiced in Central Africa (selectively), play a vital role in seed dispersal both from a qualitative and quantitative point of view.

The privilege of certified forests

As of now, it would certainly be a step too far to draw the conclusion that the gorillas show a preference for artificial felling light gaps and therefore contribute directly to the conditions necessary for regeneration of human-exploited forests. “Over the three years, I compiled three nest-site inventories: one of these was done just before the loggers had passed through the area, a second just after they had passed followed by a third 12 months later. I wanted to observe whether the gorillas showed a preference for areas that were open by logging activities. This would have given credence to the idea that when forest exploitation is practiced in a sustainable way, it is beneficial to the gorillas because it creates new habitats for them. This was not seen to be the case but this was probably because it was too early: the herbaceous plants had not yet had time to regenerate sufficiently. In my opinion, it is just a matter of time”.

If it is verified, this observation still has one major drawback. The work of Barbara Haurez was conducted in a certified forest concession. This means that the logging company has put in place a full range of measures for conservation of the flora and fauna, particularly in terms of the fight against poaching. In exchange for this, it is rewarded with a label (in this case from the FSC) certifying that it is engaged in sustainable activities. Therefore, in order to dissuade the villagers and forestry workers living in the camps from excessively hunting wild animals, they are supplied with sources of animal protein such as chicken or frozen fish. In addition, during the exploitation of designated sections of forest, surveillance teams regularly patrol the trails used by the logging trucks to prevent any poaching from taking place. Also, after use, (each parcel of the forest is exploited every twenty-five or thirty years), the pathways are closed to vehicles and so on.

It is only in conditions such as these (which are ideal on paper but, in reality, constantly being adapted -  Read : Forestry: between a rock and a hard place), that the survival of the gorilla and forestry exploitation can be declared perfectly compatible. Unfortunately, at the moment, only a minority of African Forest Concessions are certified...

Page : previous 1 2 3

 


© 2007 ULi�ge