Wildlife Corridors in the Udzungwa Mountains of Tanzania

It is widely accepted that maintaining, restoring, and protecting wildlife corridors is a critical conservation intervention at times of unprecedented habitat fragmentation (Gilbert-Norton et al. 2010). Corridors serve primarily to maintain viability of isolated populations while ensuring ecosystem functionality and harmonizing conservation and development needs (Beier and Noss 1998). Despite this importance, designing effective conservation corridors remains a challenge, and there are critical gaps between conceptual corridor research and actual corridor design and implementation (Beier and Gregory 2012). In this context, framing practical ways to design, assess functionality, and manage corridors is of priority habitat restoration relevance.

Here, we review research conducted during 2005-2010 on corridors in the Udzungwa Mountains of Tanzania. The country is one of the few for which a detailed compilation of known wildlife corridors is available at national level (Jones et al. 2009). In addition, Tanzanian wildlife policy is conducive to corridor restoration, as the 2009 Wildlife Act authorizes the Government to designate wildlife corridors and migratory routes (United Republic of Tanzania 2009). Wildlife corridors in Tanzania are classified into 5 categories, based on knowledge of wildlife movements and type of connecting habitat (Caro et al. 2009, Jones et al. 2009). The classification includes, at its extremes, 'known animal movement between two protected areas' (threatened wildlife movement criterion) and 'potential connectivity of important habitats' (fragmented habitat restoration criterion). The first type (herein Category 1) applies predominantly to large animals, often elephants (Loxodonta africana), moving across protected areas, while the second (Category 2) applies to fragmented habitat, usually highland forests, containing populations of endangered or range-restricted species.

Both of these categories of corridors have been identified in the Udzungwa Mountains. The area covers 10,000 km², comprising moist forest blocks interspersed with areas of woodland, human settlements, and agricultural areas. As the largest block of the Eastern Arc Mountains (Burgess et al. 2007), the Udzungwas hold unmatched levels of biological endemism, which are under increasing threats (Rovero et al. 2012). To the southeast of the Udzungwas, the Selous Game Reserve spans over 50,000 km² and hosts the largest population of elephants in East Africa (Figure 1). Category 1 corridors are those routes used by elephants and other large mammals to move between Udzungwa and Selous ecosystems across the Kilombero valley. Only 2 remaining routes linking these major ecosystems were identified in 2005: the Nyanganje Corridor and the Ruipa Corridor (Jones et al. 2007; Figure 1). These corridors were classified as those of 'critical urgency' by the national assessment (Jones et al. 2009), meaning that they were predicted to be closed in < 2 yrs. Remarkably, connectivity between these ecosystems is critical at a national level because the Tanzanian elephant metapopulation consists of major populations genetically interconnected via individuals moving through corridor areas (Mduma et al. 2011). The Udzungwa-Selous connection is recognized as a vital link in this network, as it is predicted to facilitate gene flow between the major western population of Ruaha-Rungwa (up to 25,000 elephants) and the major Selous-Mikumi population (up to 38,000 elephants).

The Category 2 corridor within the Udzungas is a stretch of habitat called the Mngeta Corridor, and it connects the northern forests of Udzungwa Mountains National Park and Kilombero Nature Reserve with the Uzungwa Scarp Forest Reserve (Figure 1). The latter is one of the largest (200 km²) and most threatened forests of the area, hosting many key species, particularly the Udzungwa-endemic monkeys, Sanje mangabey (Cercocebus sanjei) and Udzungwa red colobus (Procolobus gordonorum) (Rovero et al. 2012). From 2005-2010, in collaboration with various researchers, we identified, assessed, and proposed restoration measures for these corridors. The government of Tanzania has endorsed the resulting recommendations. Below is a description of these 3 corridors and the operational framework we propose for their restoration.

Figure 1.

The 2 categories of wildlife corridors assessed and proposed for restoration within the Udzungwa Mountains. The Nyanganje and Ruipa Corridors (Category 1) are indicated as dashed lines and represent large mammal routes between the Udzungwa and Selous ecosystems. The Mngeta Corridor...