The Effects of Cyclone Hudah on the Forest of Masoala Peninsula, Madagascar

Abstract

Cyclones regularly impact the east coast of Madagascar but almost nothing is known about their effects on Malagasy ecosystems. On 2 April 2000 the powerful winds of Cyclone Hudah struck the humid forests in the northern part of Masoala Peninsula. An analysis of satellite images revealed that 3% of the forest here was severely damaged or 22% when just the forest of the northeast was considered. In 2001 the vegetation in this area was studied using fifteen 0.1 ha plots located in differently impacted sites. The cyclone had caused tree death (up to 53% of the trunks within a plot); a reduction in trunk basal area (to 64%); uprooting (to 46%); snapping of trunks (to 51%); reduction of crown volume (to mean of 83%); an increase in herbs, liana and woody pioneer species and decrease in saplings of primary forest species; an increase in vegetation in the “shrub” layer and decrease in vegetation in the “canopy” layer. Among a sample of 340 trees killed by the cyclone, 39% were uprooted, 37% snapped, and 24% were still standing. Mortality was relatively low for trees with either small or large trunk diameter compared to trees with intermediate size. In 2003 the plots were re - examined. Six had been impacted by human activities (fire or timber exploitation). A comparison between the vegetation in 2001 and 2003 in 6 plots that had been moderately or seriously impacted by Cyclone Hudah but not impacted by human activity revealed a further decrease in trunk density, an increase in the frequency of herbs and woody pioneers, a decrease in the frequency of liana and saplings of primary forest trees in the “shrub layer”, and an increase of vegetation in the “shrub layer” but decrease of vegetation in the “canopy layer”. The lack of recovery of this vegetation towards its pre - cyclone state may be explained by the impact of Cyclone Ihary, in 2002. Recovery may yet occur provided the vegetation is not impacted by human activities, particularly burning, that can derail this process. It is recommended that following cyclones conservation managers prioritize fire control.