The world is losing a football pitch of soil to erosion every five seconds, according to FAO. Soil erosion is a naturally occurring process, in which the topsoil (the most fertile layer) is carried away by water, wind, or ice. It is, however, fast-tracked 100 to 1,000 times by such human activities as intensive farming, overgrazing, and deforestation, which decreases soil fertility and cropland productivity, endangering global food security in the long run.
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| Water Erosion |
A
chisel in the hands of Mother Nature, water has been sculpting its way through lands
and rocks for eons to create intricately beautiful landforms. Grand Canyon, Niagara
Falls, and Mexican cenotes are all stunning examples of water erosion. At the same time, this natural
phenomenon is accountable for about 72% of the world’s eroded soils. And, given
the effects of climate change in some regions, this figure is likely to
increase as the amount of precipitation grows. As a result, farmers are losing
the most significant resource for growing crops – topsoil – which directly
affects soil’s fertility and its potential to produce abundant yield.
What causes erosion by water
Water
erosion involves several processes: detachment, transportation, and deposition
of soil material. It is primarily triggered by several forces: rainfall and
flowing water. Depending on the intensity of rainfall, raindrops can splash
soil particles away at various, yet small distances, while runoff water further
moves them downslope. Finally, the resulting sediments are deposited in
streams, ponds, and reservoirs, where they build up over time.
Another
point to consider while looking for the roots of erosion by water is human
activities that directly and indirectly contribute to this phenomenon. Improper
irrigation of cultivated lands results in degradation of soil, which erodes
away and becomes vulnerable to flooding or waterlogging.
Farmlands left bare after intensive tillage are especially prone to erosion;
such soils lose structure and ability to properly hold plants. These are direct
causes of water erosion. Whereas glacier melt exacerbated by greenhouse gas
emissions that are massively produced by industry, transport, fossil fuel
burning, and human-induced deforestation are indirect causes.
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| Improper Irrigation Methods: A leading cause of soil erosion |
There
are a multitude of factors that determine how badly water affects soil, causing
it to erode away. These are typically related to soil type (structure,
porosity, water infiltration capacity, etc.), land topography (grade of slope),
and climate (rainfall intensity and duration). It is considered that most often
water erosion occurs in regions with steep slopes, soils having low water
infiltration rates, and poor (or no) vegetation cover.
Water-induced erosion: types and scale
Erosion
by water manifests itself in various forms depending on the magnitude and
damage extent. The most widespread types are interlinked with each other and
can be best described as several stages of a single process.
1. Splash erosion
Rain provides crops with water, which is essential for proper plant development. Raindrops, however, have an adverse effect on soil, slowly ruining its top layer. Raindrops hitting bare ground create “mini-explosions” that move soil particles away and leave tiny craters behind them. The detached soil dissolves in water and continues its way down the slope as a mud. Finally, soil gets covered with a crust and its ability to infiltrate water reduces. That’s how splash erosion occurs.
Bare
farmlands typically become an easy prey to this least impactful, yet dangerous
type of water damage since it paves way for other, more detrimental eroding
processes.
2. Sheet erosion
This water erosion type occurs whenever rainfall is so intense that soil can’t fully absorb the incoming water. The finest light particles of soil’s top layer are carried away by the sheet of excess water overflowing above the ground and further down the hill. With it, the most nutrient-rich part of soil is lost.
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| Water erosion |
In
most cases, sheet erosion hits badly crusted soils.
3. Rill erosion
If
left unattended, sheet erosion can progress to form finger-shaped channels or
rills that are usually up to 30 cm deep. More soil particles are carried away
with the water flow, intensifying damage done to soil, and eventually gullies
are formed.
4. Gully erosion
Gullies
are wide and deep trenches that develop as a result of the increased water
runoff, both in volume and speed. They typically originate from cattle burrows
and bullock cart tracks. At times, gullies can grow up to a scale where they
impede farm machinery passes or even make cropland unusable for farming. Being
one of the most advanced types of water erosion, gullies require serious
interventions in terms of restoration. Aside from soil degradation, gully
erosion also affects water quality due to high concentration of sediments that
end up in streams and larger water bodies.
5. Tunnel erosion
Also
called “hidden”, this type of water-induced soil damage erodes the subsurface,
creating underground cavities that may remain unnoticed for a long time. It
happens when water moves down through a structurally unsound soil into a hollow
space below where it keeps washing away the soil to form water-flowing tunnels.
Dispersive soils like sodosols and sodic soils that have unstable subsoil are
especially prone to tunnel erosion and eventual collapse.
Impacts of water erosion on ecosystems
Accelerated
water erosion that by far exceeds the land’s natural erosion rate leaves its
mark on both nature and human well-being.
Loss
of topsoil layer, which is most rich in organic matter, nutrients, and
microorganisms, directly affects flora. Plants growing in eroded soils with
diminished water infiltration can’t get the required amount of water and
nutrients for proper development. As a result, soil grows infertile and
croplands underproductive, affecting the income and livelihoods of farmers that
live off crops.
Another
major problem resulting from erosion by water is flooding. Compared to healthy
soils, eroded soils have reduced ability to absorb water, which increases the
risks of flooding after storms and intense rainfalls. Flood-prone regions, such
as low-lying landscapes or areas with poor soil drainage, are hit the worst. In
extreme cases, floods can sweep away roads and other infrastructure objects
disrupting transportation, supply chains, and even causing fatalities.
Water
supply itself is badly affected by water erosion. The nutrient-rich topsoil is
washed away to rivers, lakes, and reservoirs, increasing the presence of
nitrogen and phosphorus in the water (a process known as eutrophication) and
reducing its oxygen levels. Moreover, harmful pesticides from
farmlands get washed away from agricultural fields and reach neighboring
bodies. This causes pollution and further decreases water quality. Modified
chemical composition of water and presence of agrochemicals also have adverse
effects on aquatic wildlife, leading to over-the-top algae bloom and fish kill.
Keeping water erosion at bay with EOSDA Crop Monitoring
Knowing
how to prevent water erosion – for example, by maintaining proper vegetation
cover and leaving a protective layer of crop residue on top of the ground – can
help preserve soil fertility and cropland productivity. Today, the
implementation of beneficial soil conservation practices is simplified through
the use of digital precision agriculture tools. EOSDA Crop Monitoring, an
online satellite data-based tool developed by EOS Data Analytics, delivers
actionable information about fields and vegetation that helps spot and address
various types of water erosion in croplands, large and small.
An
array of vegetation indices has proven instrumental in distinguishing between
vegetated areas and bare soil, which is vulnerable to splash erosion. The
combination of Productivity maps and Scouting feature allow for precise
detection of field areas that consistently underperform over seasons and
dispatching professional scouts to check for any signs of sheet erosion, which
might be causing it.
Additionally,
EOSDA Crop Monitoring can provide a strong basis for rehabilitating farmlands
damaged by tunnel erosion. The repair requires a combined set of techniques,
including chemical amelioration and subsequent fertilizer application to
restore productivity in affected areas. The platform’s Zoning feature may add
precision and simplify the respective soil testing for chemical analysis and
variable-rate application of nutritive agents.
Water
is a powerful force that may be both beneficial and harmful to one of the
planet’s most precious and finite resources – soil. Water erosion destroys
arable lands at alarming rate and is projected to increase by 30 to 66% by
2070, exacerbated by human activities. To keep it at bay, it is necessary to
implement soil conservation practices preventing the water-induced damage.
Modern data-rich precision agriculture tools are designed to improve
soil-preserving strategies and make the implementation as simple and effective
as possible.
