Deforestation and mosquito distributions in the Amazon rainforest

Home

Steve Yanoviak
Research - Deforestation & Mosquitoes

Recent research shows that the emergence and spread of arthropod-borne tropical diseases in humans is enhanced by anthropogenic disturbance. An important next step is to understand the fundamental ecological mechanisms for this pattern. As part of a postdoctoral position at the University of Texas Medical Branch (UTMB), I managed the field operations for such a project in Peru (see Aguilar et al. 2004 pdf). Our goal was to determine how deforestation in the neotropics influences the spread of arboviral diseases, especially Venezuelan equine encephalitis (VEE). The principal investigator for the project was Dr. Scott Weaver at UTMB, and my collaborator for mosquito research on this and current projects is Dr. Phil Lounibos at the Florida Medical Entomology Laboratory. Data collection for the project was mainly accomplished by two Peruvian graduate students and eight Peruvian field assistants.

Much of the forest clearing in the western Amazon stems from subsistence agriculture and often is linked to new road construction. Deforestation proceeds over several days to weeks, during which the forest understory is removed and most of the trees felled. The site is typically burned and cultivated, resulting in a mixed plantation (or “chacra”) of pineapple, plantain, and manioc covering about a hectare. Chacras are typically managed for 3-5 years until the soil is no longer fertile. Pioneer species invading abandoned chacras during the next 5-10 years result in early successional forest called “purma”.

Aerial view near Iquitos showing how roads accelerate deforestation

Willy Chavez in old chacra/young purma habitat

Chacra planted with rice (foreground) and plantains adjacent to mature forest (background)

During most of 2001-2005, we collected mosquitoes and small mammals in each of these habitat types and in various types of mature forest near Iquitos, Peru. Adult mosquitoes were collected with a variety of traps, and Cx. gnomatos was implicated as a VEE vector (see Yanoviak et al. 2005 pdf).

Edwin Requena collecting mosquitoes from a sentinel hamster trap in a chacra

Clayder Valderrama setting up a CDC trap to catch mosquitoes in a purma

We also systematically sampled the fauna of phytotelmata in each of the habitat types. Preliminary results show that conversion of forest to chacra dramatically increases phytotelm density and enhances the production of some potential disease vectors. Results from water-filled bamboo sections suggest that the composition of top predators in phytotelmata is influenced by deforestation.

Edwin Requena collecting water from the axils of a pineapple plant

water-filled bamboo section

In a related project, we are collecting Haemagogus janthinomys mosquitoes in the forest canopy around Iquitos for possible future studies on Mayaro virus transmission. Field work for this part of the project led to the discovery of gliding ants.

J. E. Ramírez in the canopy

Haemagogus sp. mosquito

Home

Page updated 1 April 2006