全球智库信息集成服务系统

This issue brief introduces a system called FORest Monitoring for Action (FORMA), which provides near-real-time information on new forest clearing in the humid tropical forests of Asia, Africa, and Latin America. To assess FORMA’s performance, the brief compares its spatial and temporal accuracy against PRODES (Projeto de Monitoramento do Desmatamento na Amazônia Legal por Satélite) and DETER (Sistema de Detecção do Desmatamento em Tempo Real na Amazônia), two well-established systems that monitor forest clearing in the Brazilian Amazon. The assessment focuses on a rapidly deforesting area that overlaps Manicoré and Novo Aripuanã municipalities, located in the southeastern portion of the Brazilian state of Amazonas.

FORMA and DETER are both designed to identify new forest clearing at medium spatial resolution, while PRODES identifies cleared areas with higher precision on an annual basis. The assessment examines: (1) the relative spatial accuracy of FORMA and DETER against the higher-resolution annual data provided by PRODES; (2) the spatial and temporal correlation of information provided by FORMA and DETER; and (3) the possible complementarity of FORMA and DETER in predicting PRODES-identified cleared areas.

“Spatial accuracy” means the accuracy with which FORMA and DETER detect forest clearing in areas where clearing has been identified by the higher-resolution PRODES system. “Temporal accuracy” means the relative timeliness of forest clearing detection by the three systems.

In terms of spatial accuracy:

• Forest clearing areas identified by FORMA and PRODES are highly correlated. This result is consistent and stable when several statistical methods are applied.

• In the comparison of identified clearing areas, FORMA’s correlation with PRODES is significantly higher than DETER’s.

• FORMA and DETER appear to be complements rather than substitutes. A combination of DETER and FORMA detects PRODES-identified cleared areas more accurately than FORMA alone, although FORMA’s contribution to identification is greater.

In terms of temporal accuracy:

• FORMA-identified areas of new clearing consistently appear in cleared areas identified by PRODES.

• Temporal identifications of cleared areas by FORMA and DETER are highly correlated.

• In the identification of newly cleared areas, FORMA leads DETER by about half a year.

An animated demonstration of FORMA's accuracy in detecting PRODES-identified cleared areas is available for download here.