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Monday
Dec102012

Wildlife corridors vanishing in Tanzania pose threats to the survival of elephants

Conserving wildlife corridors is increasingly important for maintaining biodiversity within a population in times of unprecedented habitat fragmentation. Documenting connectivity loss, assessing root causes, and exploring restoration options are therefore priority conservation goals.

Image courtesy of Marcel O

Increased rates of urbanisation over the past three decades have seen a sharp rise in the separation of habitats, preventing the exchange of individuals between populations. This causes animals to lose both their natural habitat and the ability to move between regions of resources. A wildlife corridor is an area of habitat connecting populations that have been disrupted by human influence. The exchange of individuals between populations helps to prevent the negative effects of inbreeding and reduced genetic diversity that could occur in isolated populations.  

In Tanzania in 2009 a nationwide assessment of the wildlife corridors was undertaken. This is one of only three existing national corridor reports, the other two being from Bhutan and India. The Tanzanian assessment described 31 corridors, of which 77% were placed in categories of “extreme” or “critical” condition, meaning that they were predicted to cease within the next five years if no action was taken to restore them.

Connectivity between the Udzungwa and Selous ecosystems in Tanzania is of special conservation importance for elephants. A recent nationwide assessment of elephant corridors suggests that the major elephant populations of Tanzania are genetically interconnected via the movements of breeding individuals through corridor areas.  

Two wildlife corridors were identified in the Kilombero Valley, which is located between the Udzungwa and Selous ecosystems in Tanzania. The two most important elephant corridors acknowledged were the Nyanganje Corridor and the Ruipa Corridor. In order to indicate animal presence along the wildlife corridors surveys and assessments were undertaken, including dung and disturbance transects and land use mapping. In the Nyanganje Corridor during 2006, elephants were observed to be crossing the corridor each year from January to March. However by 2010, almost the entire Nyanganje Corridor was being used for cultivation, resulting in elephants turning back upon encountering farms and not completing their journey across the corridor. Similar patterns were seen for the Ruipa Corridor.

Image courtesy of blieusong

It has been suggested that increased farming practices, as well as an increase in the human population could be the cause for corridor blockage. However, continued attempts by elephants to cross by both routes suggest that connectivity can be restored. To restore the wildlife corridors for the elephants would entail a process of harmonizing differing land uses towards a common goal, with all land owners being fully cooperative. Management options to be considered are the private purchase of land not occupied by people; or, if a high priority area has low human density, small numbers of people may be compensated to move. A further approach would be to fence off linear sections of a corridor to funnel animals through more heavily farmed areas.

We hope that in due course these recommendations will be put into action, allowing elephants to move freely between their habitats. This research should aid the conservation of wildlife corridors all over Africa, and prevent more of them being blocked. In turn, it will increase survival rates for elephants.

By Jennifer Pearson-Farr