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Integrating local pastoral knowledge, participatory mapping, and species distribution modeling for risk assessment of invasive rubber vine (Cryptostegia grandiflora) in Ethiopia’s Afar region

“…This deep understanding of a local landscape can provide important long-term observations of ecosystem changes and the identification of nonnative species that may otherwise go unnoticed. Early detection of invasive plants is critical, and often the best response time is during the early stages of establishment when the least is known about the species-environment interactions and overall invasion potential (Kriticos et al 2003). Model outputs were consistent with ecological knowledge of the species gained from pastoralists, field observations, and existing rubber vine studies, revealing high habitat suitability across much of the interconnected riparian areas of the Awash River basin.…”

“…In Mexico, rubber vine is known to outcompete native vegetation, altering important habitat for an array of vertebrate and invertebrate species (Rodríguez-Estrella et al 2010). Although the origin of rubber vine introduction to Ethiopia is uncertain, it was introduced intentionally in other locations as an ornamental plant (Kriticos et al 2003, Rodríguez-Estrella et al 2010) and grown during World War II as a natural rubber source (Augustus et al 2000). Based on our discussions with them, pastoralists in Afar tend to agree that the vine first appeared in the middle Awash River basin within the past 20 years, concurrent with increased frequency and magnitude of flooding events.…”

“…We acquired this knowledge of hydrologic and biophysical features and human-induced disturbance drivers from a number of sources, including local pastoral knowledge, background literature reviews (Grice 1996, Brown et al 1998, Kriticos et al 2003, and field observations. We derived the Normalized Difference Vegetation Index (NDVI; Tucker 1979) from the National Aeronautics and Space Administration (NASA) Moderate Resolution Imaging Spectroradiometer (MODIS) satellite, to capture the reflectance of healthy green vegetation including rubber vine and native acacia trees that it often grows on.…”

“…For instance, the fact that Madagascar is an island quickly limits the species' dispersal capabilities. A few studies have explored rubber vine in its native range, finding its habitat to be characterized as dry tropical with highly pronounced summer rainfall (McFadyen and Harvey 1990), but Madagascar's limited climatic variation and competition between C. grandiflora and its genetically similar subspecies C. madagascariensis may belie the truly suitable climatic gradient that rubber vine can actually inhabit (Kriticos et al 2003). This point is corroborated with observational evidence in the Afar region where rubber vine is found growing in very different habitat conditions, including as a singular shrub in dry, sun-exposed dirt piles near recently disturbed agriculture fields, but also growing as extensive networks of vines, climbing up acacia trees in semishaded, cooler riparian areas.…”

“…In Australia, where the species has been established since the late 19th century, it is noted to drastically alter ecosystems and fire regimes, promoting a shift from frequent grass-dominant surface fires to infrequent but more intense crown fires (Grice 1997, Radford et al 2008. It can form dense mono-specific stands, especially in riparian areas (Kriticos et al 2003) and tolerate a range of soil conditions including sodic and saline. In Mexico, rubber vine is known to outcompete native vegetation, altering important habitat for an array of vertebrate and invertebrate species (Rodríguez-Estrella et al 2010).…”