The significance of human induced and natural erosion features (lavakas) on the central highlands of Madagascar

Abstract

Massive hill slope erosion in Madagascar is represented by the
widespread gullies called ‘lavaka’. Lavakas may be result of
natural processes that involves a combination of continuous
tectonic uplift that maintains a high angle of repose, ground
water sapping at the soil - saprolite interface, and subsequent
collapse of the soil surface due to low grade seismic activity
in the central highlands. Forest cover ranges between 25 - 45 %
in the study area and is primarily restricted to riparian and
lavaka habitats. Development of forest cover associated with
riparian and lavaka habitats may be due to increased soil
moisture, exposure of a less nutrient poor saprolite and/or
soil compaction. In addition, riparian and lavaka habitats
harbor a significantly higher diversity of plant species than the
surrounding grasslands. Lavakas may be a result of natural
processes and may play a role in the development of
Madagascar’s landscape evolution.