Context and objectives
The World Bank developed the concept of ‘environmental accounting’ (E.A.) as an essential component in its efforts to establish the basis for long-term sustainable development. The approach implies that degradation and depletion of natural resources are quantified and valued as losses in the national accounts.
The feasibility study took place in the framework of the "sustainable management plan" of the coastal zones in Kenya. It focuses on the physical approach to environmental accounting, in which sources and uses of natural resources are quantified, not valued, and are used to develop measures of environmental change and ecological stress.
The mangrove ecosystem serves as a source of several primary products used by the coastal populations and is of paramount ecological importance as breeding, feeding and nursery grounds of economically valuable fish and crustaceans. The intensive and uncontrolled exploitation of the mangroves could cause the destruction of the coastal ecosystem, and diminishes its value for energy and food production.
Expected scientific results
Taking into account the zonation and small patches in which the mangrove associations occur, it was expected that the integration of the higher spatial resolution of the SPOT P image would yield the best classification results. The study however concludes that a SPOT XS image suffices for the classification of degradation.
Some types of degradation can be determined with a monotemporal SPOT XS image set; for detection of other types of degradation, a multitemporal set is needed.
The remote sensing methodology allows for a quick and up-to-date estimation of the areas and degradation status of the important mangrove associations in the South of Kenya. The accuracy suffices for applications on a regional scale, and seems interesting in the context of ‘environmental accounting’.
For applications requiring a scale larger than 1:25.000 (such as forest management) and a high number of classes, aerial photography is the recommended information source.
A theoretical exercise shows how the information obtained from the satellite images can be incorporated in a monetary valuation of the mangrove areas, using a weight factor for the various socio-economic functions of the mangrove ecosystem.
These weight factors are not well-known, and should be determined by further research in the field.