This is a short guide listing the soil erosion rates and soil formation rates both globally, and in some different countries across the world.
This information is important to know so that we can manage topsoil and land in a sustainable way into the future.
*When we refer to soil in this guide – it’s mainly a referral to topsoil, which is the more fertile layer of soil (with decomposed organic matter, nutrients & minerals) we can use for crops and food production amongst other things
How Quickly Is Soil Loss & Erosion Occurring Worldwide?
- Half of the topsoil on the planet has been lost in the last 150 years.
- During the past 40 years nearly one-third of the world’s cropland (1.5 billion hectares) has been abandoned because of soil erosion and degradation.
- We are losing 30 soccer fields of soil every minute, mostly due to intensive farming
Soil Erosion & Formation Rates In The United States
- Between 1982 and 2007, soil erosion on U.S. cropland decreased 43%. Water (sheet & rill) erosion on cropland in 2007 declined from 1.68 billion tons per year to 960 million tons per year, and erosion due to wind declined from 1.38 billion tons per year to 765 million tons per year.
Despite the above decrease, as of 2006:
- The United States [was] losing soil 10 times faster … than the natural replenishment rate.
- In the United States alone, soil disappears 10 times faster than it is naturally replenished, according to the Cornell study, at an estimated rate of nearly 1.7 billion tons of farmland alone per year.
- The United States alone loses almost 3 tons of topsoil per acre per year
- The average soil loss rate is 5.8 tons per acre per year. Most farmers unfortunately believe their erosion loss is a fraction of that amount.
- When you’re losing soil, you’re losing yield – to the tune of about 15 bushels per acre per year of lost potential.
- [America has] lost roughly half the topsoil since farming started, but the loss is [gradual enough that is can’t be seen]
- So far, America’s farms have lost about half their soil organic matter since colonial days.
- When … European ancestors arrived [in the US], topsoil averaged around 18 inches in depth. With … intensive agricultural practices, [it’s been eroded] to around eight inches
- Each day … 30 hundred-acre farms are being lost down the river . . . 10,000 farms a year . . . 15 tons of topsoil a second . . . a yearly loss of one ton for each person on earth.
- … America have lost about one-third of … arable land since people arrived there.
- At [the current rate] another third [will be lost] in the next dozen or so years, while the population almost doubles.
Soil Erosion & Formation Rates In China
As of 2006:
- China [was] losing soil 30 to 40 times faster … than the natural replenishment rate.
Soil Erosion & Formation Rates In India
As of 2006:
- India [was] losing soil 30 to 40 times faster … than the natural replenishment rate.
Soil Erosion & Formation Rates In Australia
- Soil formation rates in some parts of Australia are below global averages
- Soil erosion rates and soil protection measures have improved in Victoria and South Australia over the last few decades
- Current rates of soil erosion by water across much of Australia now exceed soil formation rates
- Wind erosion rates can differ with annual climatic variation
- Generally, soil erosion across Australia rates as poor to good, on a scale from very poor to very good
How Quickly Does Soil Form/Renew Itself On Average?
- The current high erosion rates throughout the world are of great concern because of the slow rate of topsoil renewal; it takes approximately 500 years for 2.5 cm layer of fertile topsoil to form under agricultural conditions.
- Generating three centimeters of top soil takes 1,000 years, and if current rates of degradation continue all of the world’s top soil could be gone within 60 years
- Under the best case scenario, soil can only rebuild at a rate of 0.24 tons per acre per year.
But, it can depend on the soil type, rock type, climate, environment and part of the world.
Parts of Australia are examples of where soil formation fall below the average renewal rate:
- Soil formation from weathering rock is slower [than dune sands in moist environments], and varies with the environment and rock type
- An average of about 10 millimetres per 1000 years is typical in New South Wales, increasing to about 75 millimetres per 1000 years in Arnhem Land, Northern Territory. These soil formation rates are low compared with the estimated global average of 114 millimetres per 1000 years
A Note On Soil Loss Trends & Overall Soil Replacement Rates
As can be seen from the data above, it’s possible for a country or region in the world to decrease their soil erosion rates via soil conservation measures, but still be losing soil at a greater rate than the soil replacement rate.