Action: Plant indigenous trees to re-establish natural tree communities in clear-cut areas
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- One site comparison study in Kenya found that two out of three primate species had lower group densities in planted forests than in natural forests.
This intervention involves the planting of indigenous trees to re-establish natural tree communities after clear-cutting. It should be noted, however, that planting trees will almost always be more expensive than preserving natural forests from clear-cutting and that natural forests are usually more suitable as habitat for a wider range of native forest species than plantation forests (which is not to say that primates cannot survive in young regrowth forest). In addition, it can take centuries and even millennia for the forest to regrow to its pre-disturbance state. For example, an Atlantic rainforest needs about one to three hundred years to reach the proportion of animal-dispersed species (80% of the species), the proportion of non-pioneer species (90%) and of understorey species (50%) found in mature forests. On the other hand, much more time is necessary (between one and four thousand years) to reach the endemism levels (40% of the species) that exist in mature forests (Liebsch et al. 2008). Therefore, this intervention should only be considered if the natural habitat is already lost or if preserving it will not be possible.
Liebsch D., Marques M.C.M. & Goldenberg R. (2008) How long does the Atlantic Rain Forest take to recover after a disturbance? Changes in species composition and ecological features during secondary succession. Biological Conservation, 141, 1717–1725.
Supporting evidence from individual studies
A site comparison in 2006-2010 in natural and planted forest in Kakamega Forest, Kenya found that black and white colobus Colobus guereza achieved similar average group densities but smaller group size in planted as in natural forest but group densities of blue monkey Cercopithecus mitis and redtail monkey Cercopithecus ascanius were 42-45% lower in planted forest than in natural forest. Black and white colobus average group sizes in planted forest were 33% smaller than in natural forest, resulting in a population that was 35% smaller in size compared to those in natural forest. No statistical tests were carried out to determine whether these differences were significant. Natural forest included old secondary forest that connected to the remaining natural old-growth forest. Planted forest included mixed indigenous trees planted in 1930-1940 in areas where natural vegetation had been clear-cut. Monkey density was estimated based on transect observations in both forest types using the ‘Whitesides’ and ‘Distance’ methods. Transects followed pre-existing footpaths or dirt roads.