Brigitte Portner

Environmental conditions and human drivers for changes to north Ethiopian mountain landscapes over 145 years

As quantitative or spatially distributed studies of environmental change over truly long-term periods of more than 100 years are extremely rare, we re-photographed 361 landscapes that appear on historical photographs (1868-1994) within a 40,000 km(2) study area in northern Ethiopia. Visible evidence of environmental changes apparent from the paired photographs was analyzed using an expert rating system. The conditions of the woody vegetation, soil and water conservation structures and land management were worse in the earlier periods compared to their present conditions. The cover by indigenous trees is a notable exception: it peaked in the 1930s, declined afterwards and then achieved a second peak in the early 21st century. Particularly in areas with greater population densities, there has been a significant increase in woody vegetation and soil and water conservation structures over the course of the study period. We conclude that except for an apparent upward movement of the upper tree limit, the direct human impacts on the environment are overriding the effects of climate change in the north Ethiopian highlands and that the northern Ethiopian highlands are currently greener than at any other time in the last 145 years.

Soil erosion and conservation in global agriculture

About one-sixth of the world’s land area, that is, about one-third of the land used for agriculture, has been affected by soil degradation in the historic past. While most of this damage was caused by water and wind erosion, other forms of soil degradation are induced by biological, chemical, and physical processes. Since the 1950s, pressure on agricultural land has increased considerably owing to population growth and agricultural modernization. Small-scale farming is the largest occupation in the world, involving over 2.5 billion people, over 70% of whom live below the poverty line. Soil erosion, along with other environmental threats, particularly affects these farmers by diminishing yields that are primarily used for subsistence. Soil and water conservation measures have been developed and applied on many farms. Local and science-based innovations are available for most agroecological conditions and land management and farming types. Principles and measures developed for small-scale as well as modern agricultural systems have begun to show positive impacts in most regions of the world, particularly in wealthier states and modern systems. Much more emphasis still needs to be given to small-scale farming, which requires external support for investment in sustainable land management technologies as an indispensable and integral component of farm activities.

Effectiveness of jatropha barriers as a soil and water conservation technology to rehabilitate gullies in northern Ethiopia

Jatropha (Jatropha curcas L.), a perennial oil-producing shrub, has been promoted in many parts of sub-Saharan Africa in recent years, with the aim of producing biofuels, developing rural areas, and providing alternative income opportunities (Francis et al. 2005). Researchers largely agree that jatropha is suited for rehabilitating degraded land, as it improves microbial activity, available nutrients, and water holding in soils (Wani et al. 2012). The basic pattern of its root structure is believed to control soil erosion (Achten et al. 2007), although in drylands limited water availability has negative effects on jatropha root growth and overall performance (Krishnamurthy et al. 2012). Nonetheless, only few studies investigate vegetative soil and water conservation technologies based on jatropha. Rare individual studies, such as the ones by Openshaw (2000) on hedges or by Kagamebga et al. (2011) on the half-moon technique in Burkina Faso, demonstrate that jatropha can, in different ways, successfully be used for soil and water conservation. In the Ethiopian Highlands, land degradation is a major concern, and the control and rehabilitation of gullies pose a particular challenge. Efforts to conserve soil and water have been made for a long time and at a large scale (Dale 2010). However, farmers often…