A New Map of Standardized Terrestrial Ecosystems of Africa

Terrestrial ecosystems and vegetation of Africa were classified and mapped as part of a larger effort and global protocol (GEOSS – the Global Earth Observation System of Systems), which includes an activity to map terrestrial ecosystems of the earth in a standardized, robust, and practical manner, and at the finest possible spatial resolution. To model the potential distribution of ecosystems, new continental datasets for several key physical environment datalayers (including coastline, landforms, surficial lithology, and bioclimates) were developed at spatial and classification resolutions finer than existing similar datalayers. A hierarchical vegetation classification was developed by African ecosystem scientists and vegetation geographers, who also provided sample locations of the newly classified vegetation units. The vegetation types and ecosystems were then mapped across the continent using a classification and regression tree (CART) inductive model, which predicted the potential distribution of vegetation types from a suite of biophysical environmental attributes including bioclimate region, biogeographic region, surficial lithology, landform, elevation and land cover. Multi-scale ecosystems were classified and mapped in an increasingly detailed hierarchical framework using vegetation-based concepts of class, subclass, formation, division, and macrogroup levels. The finest vegetation units (macrogroups) classified and mapped in this effort are defined using diagnostic plant species and diagnostic growth forms that reflect biogeographic differences in composition and sub-continental to regional differences in mesoclimate, geology, substrates, hydrology, and disturbance regimes (FGDC, 2008). The macrogroups are regarded as meso-scale (100s to 10,000s of hectares) ecosystems. A total of 126 macrogroup types were mapped, each with multiple, repeating occurrences on the landscape. The modeling effort was implemented at a base spatial resolution of 90 m. In addition to creating several rich, new continent-wide biophysical datalayers describing African vegetation and ecosystems, our intention was to explore feasible approaches to rapidly moving this type of standardized, continent-wide, ecosystem classification and mapping effort forward. In 2005, a consortium of nations, the Group on Earth Observations (GEO), convened and created the Global Earth Observation System of Systems (GEOSS). GEOSS is an intergovernmental protocol aimed at promoting and facilitating the use of earth observations, both in-situ and remotely-sensed, for societal benefit. GEOSS is programmatically organized into nine societal benefit areas (ecosystems, biodiversity, weather, disasters, health, water, energy, climate, and agriculture). The ecosystems societal benefit area includes a task (EC-01-C1) to develop a standardized, robust, and practical classification and map of global ecosystems (Sayre et al., 2007). This task is currently described in the GEOSS 2012-2015 work plan.1 It was originally commissioned in the initial framework GEOSS ten year work plan.2 The methodology for producing these standardized terrestrial ecosystems has previously been implemented for South America (Sayre et al., 2008) and the United States (Sayre et al., 2009) and was adapted for Africa as described below. Numerous ecological regionalizations of Africa exist. Notable among them are the biogeographical provinces of Udvardy (1975), the pioneering work of Frank White (1983) to map phytochorological regions (based on the number of endemic species), the phytogeographic maps (floristic regions) of Takhtajan (1986), and more recently the terrestrial ecoregions of Bailey (1998) and the World Wildlife Fund (Burgess et al., 2004). These interpretive efforts, drawing extensively upon expert knowledge and intuitive boundary demarcation, have considerably advanced the understanding of African ecogeography. A potential vegetation map extending White’s (1983) chorological emphasis in greater detail across seven east African countries has been produced as part of a seven volume monograph series and atlas (Lillesø et al., 2011). Remote sensing-derived maps of regional and global land cover such as those from the Africover (FAO, 1997), Global Land Cover 2000 (Mayaux et al., 2006) and the GlobCover 2005 (Bicheron at al., 2006) products have similarly provided increasingly quantitative and finer spatial resolution characterizations of vegetation cover for A New Map of Standardized Terrestrial Ecosystems of Africa A Special Supplement to the African Geographical Review 5 Africa. The work described herein represents a new effort to model African ecosystem distributions across the entire continent at a 90m base resolution using physical environment data and geospatial statistics.