Large Scale Afforestation in Arid and Semi-Arid Climate: Hydrologic-Ecological Lessons Learned and Concept of Modular Hydrologic Connectivity of Vegetation
Schulze-Delitzsch-Str. 8, D-24943 Flensburg, Germany, Lorenz Huebner
Abstract
We present selected key ecological and hydrological lessons learned from large scale afforestation in arid andsemi-arid areas on three continents. Compact dense large scale afforestation often was shown to be too massive for thisclimate zone, resulting in hydrological and ecological issues. Most alarming findings were those of overuse of water withincreasing age of plantation, too dense planting and selecting not native or not adapted species. Planting campaigns inChina started 40 years ago, aimed to mitigate dust storms. In some semi-arid regions, severe worsening of thehydrological situation resulted in a high rate of tree mortality. However, a very positive outcome is reported for an exampleregion 60 years after the start of first plantations, here connective tree belts serve as a biophysical barrier and therebyhave induced transformation to moderately sub-humid climate.Based on the learnings and in analogy to “ecological connectivity” of biotopes, a non-invasive concept of “hydrologicconnectivity” of vegetation in dry desertification areas is suggested as an alternative to massive large scale afforestation.In a “climate connective network”, vegetation belts will serve as “hydrological corridors” to keep up the humidity of air andsoil between any area of vegetation to optimize the self-supportive climatic feedback of new large scale vegetation. Toavoid overuse of water, natural succession areas of grass- and bushland (with high soil moisture content) are flanked bynative shrub or tree belts causing windbreak and increased air humidity in the corridors. This modular concept of climaticconnectivity could help to enhance vegetation in a time and cost-effective way, it allows for natural succession and mayavoid hydrological and ecological pitfalls of earlier plantations.The concept maximizes regional plant induced mitigation of climate, e.g. in the context of large scale renaturationprojects. Shrub or tree-related reduction in albedo is around 15% of that of massive green belts.