Biodeterioration of historical buildings and sites in north of Lake Tana, Ethiopia: a preliminary investigation

Lake Tana is the largest lake in Ethiopia and the source of the Blue Nile. The lake is protected as a natural heritage site. It is surrounded by wetlands that provide a sanctuary to a diverse set of flora and fauna some of which are endemic to the region. It is also a culturally significant area. Surrounding the lake and on the islands are found tens of stone built monasteries, churches, bridges and palaces built in the Gondarine period (17^th and 18^th Century AD) and earlier. However, these buildings are subjected to biological growth in many different types that cause  discoloration and  degradation. The short and intense rainy season contributes to the nature, diversity and intensity of biological colonization of these stone structures. Biofilms, fungi, mosses, lichen and higher plants can be observed, while also small animals such as mites and rodents are agents of bio-deteriorative process. While micro-organisms alter the visual appearance, roots of higher plants are responsible for more severe physical decay on the site and building level, increasing also the impact of moisture-related weathering in decayed locations. However, micro-organisms can also alter the surface properties of materials, like water absorption and retention, and it is currently not well understood to what extend these contribute to the observed forms of degradation, like chipping, fissuring, cracking, etc. 

This poster aims to address some of the key challenges of managing cultural heritage sites found in a complex, evolving and vulnerable ecosystem, i.e. Lake Tana. Factors such as intense rainfall, humidity, the state of the structures, intensification of agriculture and the perspectives of local communities and stakeholders will be evaluated.