Soil erosion is a major environmental threat to the sustainability and productive capacity of agriculture. During the last 40 years, nearly one-third of the world's arable land has been lost by erosion and continues to be lost at a rate of more than 10 million hectares per year. With the addition of a quarter of a million people each day, the world population's food demand is increasing at a time when per capita food productivity is beginning to decline.

https://science.sciencemag.org/content/sci/267/5201/1117.full.pdf

Environmental and Economic Costs of Soil Erosion and Conservation Benefits

Human activity and related land use change are the primary cause of accelerated soil erosion, which has substantial implications for nutrient and carbon cycling, land productivity and in turn, worldwide socio-economic conditions. Here we present an unprecedentedly high resolution (250 × 250 m) global potential soil erosion model, using a combination of remote sensing, GIS modelling and census data. We challenge the previous annual soil erosion reference values as our estimate, of 35.9 Pg yr−1 of soil eroded in 2012, is at least two times lower. Moreover, we estimate the spatial and temporal effects of land use change between 2001 and 2012 and the potential offset of the global application of conservation practices. Our findings indicate a potential overall increase in global soil erosion driven by cropland expansion. The greatest increases are predicted to occur in Sub-Saharan Africa, South America and Southeast Asia. The least developed economies have been found to experience the highest estimates of soil erosion rates.

/pdf/an-assessment-of-the-global-impact-of-21st-century-land-use-rdg7ojdzqi.pdf

An assessment of the global impact of 21st century land use change on soil erosion.

Soil erosion is a global issue because of its severe adverse economic and environmental impacts. Economic impacts on productivity may be due to direct effects on crops/plants on-site and off-site, and environmental consequences are primarily off-site due either to pollution of natural waters or adverse effects on air quality due to dust and emissions of radiatively active gases. Off-site economic effects of erosion are related to the damage to civil structure, siltation of water ways and reservoirs, and additional costs involved in water treatment. There are numerous reports regarding the on-site effects of erosion on productivity. However, a vast majority of these are from the U.S., Canada, Australia, and Europe, and only a few from soils of the tropics and subtropics. On-site effects of erosion on agronomic productivity are assessed with a wide range of methods, which can be broadly grouped into three categories: agronomic/soil quality evaluation, economic assessment, and knowledge surveys. Agronomic me...

Soil Erosion Impact on Agronomic Productivity and Environment Quality

Sedimentation and turbidity are significant contributors to declines in populations of North American aquatic organisms. Impacts to lotic fauna may be expressed through pervasive alterations in local food chains beginning at the primary trophic level. Decreases in primary production are associated with increases in sedimentation and turbidity and produce negative cascading effects through depleted food availability to zooplankton, insects, freshwater mollusks, and fish. Direct effects at each trophic level are mortality, reduced physiological function, and avoidance; however, decreases in available food at trophic levels also result in depressed rates of growth, reproduction, and recruitment. Impacts of turbidity to aquatic organisms often seem inconsistent among watersheds and experiments, but this apparent difference is actually due to the lack of correlation between suspended sediment concentrations (mg/L) and units of measure (Nephelometric Turbidity Units, NTU). The use of NTU as a surrogate measurem...

/pdf/effects-of-sedimentation-and-turbidity-on-lotic-food-webs-a-4osf5l41tj.pdf

Effects of sedimentation and turbidity on lotic food webs: a concise review for natural resource managers

Riparian buffer zones (RBZ) improve water quality in different ways depending upon the pathway of delivery of water to the RBZ. Groundwater passing through the RBZ may be cleansed of nitrate and acidity due to a combination of denitrification, biostorage and changes in soil composition. Overland storm flows entering laterally from the uplands may be cleansed of suspended particulates, with adhering nutrients, inorganic toxins, and pesticides, as well as some dissolved nutrients and toxins. Sometimes these overland flows will also infiltrate within the RBZ and become a part of the groundwater, thus also obtaining the benefits associated with groundwaters in the RBZ. During stream flooding events, waters flooding out into the RBZ may also be cleansed of sediments, nutrients and toxic materials as a result of particulate trapping and the binding of materials on the leaf litter and soils within the RBZ. The RBZ is also an important source to the stream of high quality dissolved and particulate organic matter which is delivered both vertically and laterally. Forested RBZs also provide shade and evaporative cooling to streams, maintaining lower summertime temperatures critical to some biota. Factors which limit the effectiveness of the functions can be divided into internal and external. Factors external to the RBZ include watershed area and gradient, stream channel morphology, soil mineralogy and texture, bedrock type and depth, and climate. Factors internal to the RBZ include width and type of vegetation, waterlogging and organic content of soils, hydraulic conductivity, soil nutrient content and geochemistry. These water quality functions of RBZs and the factors which limit their effectiveness in various settings are reviewed from the world literature. INTRODUCTION Only a few papers which explicitly reported the results of studies of the water quality buffering effects of vegetated riparian zones were published prior to the early 1970s (Fig. 1). Although it is very difficult to draw sharp boundaries around this subject, there are now over 400 such papers and the rate of publication is about 30 to 35 papers per year. Despite this increasing rate of publication, our knowledge base concerning the water quality buffering effects of riparian zones is far from adequate. For descriptive aspects such as the removal of nitrate and particulate matter from the waters traversing the riparian zone or the release of organic matter to these waters we have considerable data but lack knowledge for how these functions change with climate or watershed management; species composition and age of the plant community; or how and when these functions will be saturated or exceeded. More fundamentally, we usually do not have an adequate understanding of the basic mechanisms involved in these processes or the controls over the rates of these processes. Lacking this understanding of mechanisms, we are in danger of being overconfident of our ability to predict system behaviour and response to major changes in inputs, invasions by exotic biota, or altered climate. With this situation in mind I will endeavour to review the world literature on riparian buffer zones, with my emphasis on streams and water quality. If we look at riparian vegetation and the soils in which they grow as a part of the landscape (Lowrance et al., 1985; Jordan et al., 1986; Correll et al., 1992), we can examine factors that control the health and functioning of these ecosystems and delimit them spatially. Some of these factors are internal or 7 Buffer Zones: Their Processes and Potential in Water Protection. Edited by N.E. Haycock, T.P. Burt, K.W.T. Goulding and G. Pinay. ISBN 0 9530051 0 0 © 1997 Quest Environmental. 2

Buffer zones: their processes and potential in water protection

MANY studies document the damage that sediment, nutrients, and other soil erosion-related pollutants cause in streams, lakes, reservoirs, and estuaries, but few studies attempt to calculate the economic costs of these damages. All recent economic studies are limited in the damage they consider, their geographic scopes, or, most commonly, both. The last estimate of national economic costs associated with erosion-related damages was made in 1946 ( 1 ). The Conservation Foundation recently completed a study that attempts to fill this gap ( 3 ).

Any such attempt must grapple with numerous problems. Many damages are only weakly documented. If the damages are well documented, the linkage between them and soil erosion is probably not. Even if the damages and linkages are known, it is difficult to assign economic values to the damages. Thus, the estimates given here are indicative, not definitive.

Instream damages 

Instream damages are those caused by sediment, nutrients, and other erosion-related contaminants in streams and lakes. These include damages to aquatic organisms, water-based recreation, water storage facilities, and navigation

Biological impacts . Aquatic ecosystems can be seriously affected by sediment and other erosion-related contaminants in complex ways. Sediment can destroy spawning areas, food sources, and habitat as …

Edwin H. Clark

Papers

The off-site costs of soil erosion