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Water and Wind Erosion
Studies dealing with water- and wind-affected land degradation are major subjects under investigation at the BIDR. Scientists of the Meteorology Group have set up six major dust collection stations, which help evaluate the wind-engendered erosion of surface material. Modeling of the production, transport and deposit of atmospheric dust is under study through theoretical approaches as well as by field and wind tunnel experiments. An improved understanding of atmospheric dust is important for environmental conservation, as well as for dryland agriculture and solar energy exploitation.
Badlands are extremely barren arid terrains where water and wind erosion have cut deep gullies and ravines through soft rocks and soil. Researchers at the Ramon Science Center are probing the formation of and deepening of gullies in Israel’s Negev Highland region. Because this land is presently under use for agriculture and ranging, an evaluation of the advance of gully erosion in drainage basins is vital for preserving the economic value of this region. The researchers measured soil loss and vegetation decrease in valleys containing actively forming gullies, processes severely reducing the agricultural and range potential of the affected land. If allowed to continue its slow progress, the Negev Highlands would turn into unusable badlands within a few millennia. Fortunately, there are proven techniques to halt gully advance by strengthening gully catchments to decrease peek runoff flow, by diverting surface water flow above the gully area, by building stabilizing structures to prevent gully advance, and by revegetation. Some of these approaches are already being adopted to retard erosion in the Highlands.
Badlands at Nahal Kevuda in the Western Negev. Photo by Hezi Yizhaq.
Plant-Cover Protection
Plant cover is a major factor that protects land against desertification. Both native trees and low ground vegetation, which have developed the ability to grow in low precipitation regions, have their roles to play. Plant roots stabilize the ground against runoff damage and plant leaves provide an excellent natural windbreaks.
A. Trees
Studying the role of trees in drylands, researchers in the Blaustein Institute’s Wyler Department of Dryland Agriculture are probing forest growth as related to water movement into, out of, and within dryland forests. Because water is the crucial factor supporting tree growth in semi-arid regions, these water balance determinations are essential for evaluating the sustainability of forested areas. Studying the Yatir Forest, northeast of Beer-Sheva, the BIDR team found that the extremely sparse tree canopy hardly intercepts rainfall, with almost all precipitation reaching the ground and supporting plant growth. In addition, rainfall runoff entering the forest is stored in the ground and does not leave. Therefore, practically all the rainwater and runoff is stored in the soil and is later used by trees and low annual herbs growing among them. These results confirm the importance of planting forests in arid regions to prevent desertification.
View of Yatir Forest, with the Negev desert in the background.
B. Shrubs
In related BIDR investigations, the use of the gathering of runoff to support forests and crops planted in arid regions has been advanced in various countries. This form of agriculture, known as agroforestry, has been practiced all over the world for thousands of years. BIDR projects, applying up-to-date techniques in designing and studying forests for raising human and animal crops, is aiding farmers and pastoralists in the drylands of Israel, Kenya, Turkmenistan, and Uzbekistan.
Low ground plants also have their roles in stabilizing drylands from erosion. Researchers in the BIDR Department of Solar Energy and Environmental Physics are investigating the growth and pattern formation characteristic of vegetation in drylands. When precipitation is high, ground plants provide a uniform protective cover. But when climatic changes lead to a steady decrease in annual rainfall, the soil starts showing bare spots, plants begin growing first in banded patterns, patches that become increasingly distant from one another. When water availability falls below a critical level, vegetative propagation fails and the soil turns bare, a condition of severe desertification.
The BIDR environmental physicists have developed a mathematical model that, along with field measurements, seeks to clarify the processes underlying vegetation patterning and to discover ways of rehabilitating dryland regions undergoing desertification. The model also aids the management of water and soil resources in order to preserve plant vitality.
Based on observations and experimental data, the team has constructed a conceptual model that defines the components required to describe the desert biome. These include its organisms (plants, animals), resources (water, nutrients, solar radiation), and landscape (soil type, topography) relevant to the region under study. This mathematical model can predict how these factors will affect the appearance of vegetation patterns, and has been applied to understand the appearance of desertification. The predictive value of the model has been demonstrated by using it to confirm the vegetative patterns observed in various Negev and other locales.
The model also revealed a previously unrecognized aspect of desertification. When precipitation drops, existing plants can continue to survive in a characteristic patterned structure. However, if it drops below a certain level and the land turns bare, a return to the previous vegetation supporting situation is not possible, and much greater precipitation levels are required to enable the region to reach its former vegetation status. Therefore, as desertification intensifies, steps must be taken to enhance water availability to poorly vegetated regions before they dry up.
C. Mathematical Modeling of Vegetation Growth
Researchers in the BIDR Department of Solar Energy and Environmental Physics are investigating the growth and
pattern formation characteristic of vegetation in drylands. When precipitation is high, ground plants provide a uniform protective cover. But when climatic changes lead to a steady decrease in annual rainfall, the soil starts showing bare spots, then plants begin growing in banded patterns, followed by the formation of spots that become increasingly distant from one another. When water availability falls below a critical level, vegetative propagation fails and the soil turns bare, a condition of severe desertification.
The BIDR environmental physicists have developed a mathematical model that, along with field measurements, seeks to clarify the processes underlying vegetation patterning and to discover ways of rehabilitating dryland regions undergoing desertification. The model also aids the management of water and soil resources in order to preserve plant vitality.
Based on observations and experimental data, the team has constructed a conceptual model that defines the components required to describe the desert biome. These include its organisms (plants, animals), resources (water, nutrients, solar radiation), and landscape (soil type, topography) relevant to the region under study. This mathematical model enables the determination of how these factors effect the appearance of vegetation patterns, and has been applied to understand the appearance of desertification. The predictive value of the model has been demonstrated by using it to confirm the vegetative patterns observed in various Negev and other locales. To observe how vegetation growth patterns change with time at different precipitation levels, click here.
The model also revealed a previously unrecognized aspect of desertification. Namely, when precipitation drops to a particular level, existing plants can continue to survive in a characteristic patterned structure. However, if rainfall drops too low and the land turns bare, a return to the previous vegetation supporting situation is not possible. Much greater precipitation levels are required to enable the region to reach its former vegetation status. Therefore, as desertification intensifies, steps must be taken to enhance water availability to poorly vegetated regions before they dry up.
Land Degeneration via Human Overexploitation
Human agricultural and pastoral activities are well-documented factors contributing to desertification. In order to halt and reverse man-engendered land degeneration, a basic understanding of dryland societies is required, along with data on the changes occurring in the soil and natural vegetation they exploit. At the Wyler Department of Dryland Agriculture, the effects of livestock browsing were investigated in detail, providing an improved knowledge of how ranging effects the diversity and composition of annual plant communities in drylands. These studies can provide training for pastoralists as how to better preserve their natural grazing grounds.
At the BIDR Department of Man in the Desert, nomadic pastoral societies in Israel, Africa, and Asia are under study in order to design socially acceptable strategies to ameliorate creeping desertification caused by overgrazing and by climatic changes that reduce precipitation. To protect damage to range areas, programs are being instituted that advance residents’ management of available resources, particularly the use of runoff harvesting for increased crop cultivation and fodder production in drought years. In addition, improved drought-resistant plant strains are under development at the BIDR — including wheat, yams, fodder shrubs, and cotton — that could help expand agriculture in arid regions.
Intercropping in Kenya.
Women in Desert Societies
Because women are major participants in dryland grazing and farming, they must also be active in development projects aimed at increasing the efficient use of rural resources required for these endeavors, such as land, water, and livestock. One researcher at theDepartment of Man in the Desert has investigated the sociology of women of the Tswana and Basarwa communities in Botswana, who were affected by development programs established for these communities. The positive and negative impacts of the land reform policies on women and attempts to bring the communities up to first-world status of equality and rights were reviewed. Lessons from this work are being applied to a major international project for promoting a sustainable agricultural development in the arid regions of Israel, Jordan, Egypt and the Palestinian Authority. Participants have produced a comprehensive review of gaps in data regarding local women’s participation in agriculture. Strategies were proposed to support the active involvement of women in specific agricultural projects. This activity could go far to improve the development of agriculture in Israel and its surrounding areas, as well as provide a testing ground for activities in other countries.
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