We present selected key ecological and hydrological lessons learned from large scale afforestation in arid and semi-arid areas on three continents. Compact dense large scale afforestation often was shown to be too massive for this climate zone, resulting in hydrological and ecological issues. Most alarming findings were those of overuse of water with increasing age of plantation, too dense planting and selecting not native or not adapted species. Planting campaigns in China started 40 years ago, aimed to mitigate dust storms. In some semi-arid regions, severe worsening of the hydrological situation resulted in a high rate of tree mortality. However, a very positive outcome is reported for an example region 60 years after the start of first plantations, here connective tree belts serve as a biophysical barrier and thereby have induced transformation to moderately sub-humid climate.Based on the learnings and in analogy to "ecological connectivity" of biotopes, a non-invasive concept of "hydrologic connectivity" 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 and soil between any area of vegetation to optimize the self-supportive climatic feedback of new large scale vegetation. To avoid overuse of water, natural succession areas of grass-and bushland (with high soil moisture content) are flanked by native shrub or tree belts causing windbreak and increased air humidity in the corridors. This modular concept of climatic connectivity could help to enhance vegetation in a time and cost-effective way, it allows for natural succession and may avoid hydrological and ecological pitfalls of earlier plantations.The concept maximizes regional plant induced mitigation of climate, e.g. in the context of large scale renaturation projects. Shrub or tree-related reduction in albedo is around 15% of that of massive green belts.
In the past two decades, severe drought has been a recurrent problem in Iraq due in part to climate change. Additionally, the catastrophic drop in the discharge of the Tigris and Euphrates rivers and their tributaries has aggravated the drought situation in Iraq, which was formerly one of the most water-rich nations in the Middle East. The Kurdistan Region of Iraq (KRI) also has catastrophic drought conditions. This study analyzed a Landsat time-series dataset from 1998 to 2021 to determine the drought severity status in the KRI. The Modified Soil-Adjusted Vegetation Index (MSAVI2) and Normalized Difference Water Index (NDWI) were used as spectral-based drought indices to evaluate the severity of the drought and study the changes in vegetative cover, water bodies, and precipitation. The Standardized Precipitation Index (SPI) and the Spatial Coefficient of Variation (CV) were used as meteorologically based drought indices. According to this study, the study area had precipitation deficits and severe droughts in 2000, 2008, 2012, and 2021. The MSAVI2 results indicated that the vegetative cover decreased by 36.4%, 39.8%, and 46.3% in 2000, 2008, and 2012, respectively. The SPI’s results indicated that the KRI experienced droughts in 1999, 2000, 2008, 2009, 2012, and 2021, while the southeastern part of the KRI was most affected by drought in 2008. In 2012, the KRI’s western and southern parts were also considerably affected by drought. Furthermore, Lake Dukan (LD), which lost 63.9% of its surface area in 1999, experienced the most remarkable shrinkage among water bodies. Analysis of the geographic distribution of the CV of annual precipitation indicated that the northeastern parts, which get much more precipitation, had less spatial rainfall variability and more uniform distribution throughout the year than other areas. Moreover, the southwest parts exhibited a higher fluctuation in annual spatial variation. There was a statistically significant positive correlation between MSAVI2, SPI, NDWI, and agricultural yield-based vegetation cover. The results also revealed that low precipitation rates are always associated with declining crop yields and LD shrinkage. These findings may be concluded to provide policymakers in the KRI with a scientific foundation for agricultural preservation and drought mitigation.
It is a great concept to let nature do the work of revegetation, however in semi-arid and arid regions the process of natural succession, if it occurs at all, typically requires many years of undisturbed development until an increase in biomass becomes measurable, hence it rather is applied to remote, sparsely populated regions and may be underrated as a measure to restore native vegetation, particularly in inhabited arid areas. What are the factors that make arid successional processes successful, how to expedite, and how to enable their use for the ecological revegetation of densely populated drylands? We review restoration methods that combine the planting of shelterbelt compartments with successional revegetation of the internal area, protected from wind and drought. Various measures of assisted natural succession can be applied to greatly accelerate the revegetation, including soil tillage, amendment with organic matter and the inoculation with cyanobacteria or lichens to form biocrusts. The aim is to initiate the development of native, water-saving savanna with biodiversity, resilience and adaptability to climate change. A narrow twin shelterbelt module could facilitate the use of natural succession within inhabited and peri-urban areas, also serving as protective greenbelt for cities. A pilot is planned in a peri-urban area of Northern Iraq, with a successional area of 125–150 m between shelterbelts. Land-use of agriculture, gardening and recreation can be integrated within the successional area, which also generates engagement of residents in the maintenance work. Planting of shelterbelts is required on 10–25% (not 100%) of the restoration area, therefore the use of assisted succession within protective compartments is expected to have both, ecological and economic advantages over large-scale afforestation.
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