Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Overgrazing accelerating soil erosion in northern Mexico

08.01.2008
Every year in the world an estimated 20 million hectares of arable land are rendered infertile simply owing to water-induced erosion. It is therefore crucial to understand how these processes arise in order better to protect the layer of a few tens of metres of fertile soil essential for plant growth and therefore for sustaining agriculture. In the North of Mexico, about ten years ago IRD teams studied the erosion phenomenon which affects this region where pastoral activities and tree felling aggravate the process.

As part of field studies conducted from 1993 to 2000 on the mountain crests of the western Sierra Madre and in the more arid regions in the south of the Chihuahua Desert, the scientific team established a soil classification according to climatic and topographic characteristics. They used a rainfall index type hydrological model which gives real-time simulation of the humidity state of soil on the basis of a range of parameters including soil humidity, runoff rate, water storage capacity.

This measurement method also takes into account the volume of rain collected at a given moment and the time lapsed since it fell. This model, named NAZASM, with reference to the Rio Nazas drainage basin where it was first used in 1999, provides a means of classifying each soil type according to the processes that allow infiltration of water but also its runoff on the surface. From pine and oak forests of the Sierra’s mountains, to the bare expanses of the Chihuahua Desert located at 1000 m altitude, the rainfall was determined, varying locally from 1000 mm to less than 200 mm. The NAZASM model led to the assessment that only the drainage basins of the sub-humid zone of the western Sierra Madre had the capacity to let the rainwater pass through the soil before part of it could flow into water courses.

The soil degradation associated with overgrazing could substantially reduce this storage capacity. In the other, arid or semi-arid type terrains studied, the soil infiltration capacity was most often lower than the rainfall rate. That is translated by the formation of runoff on the soil surface and this accentuates the process of water erosion.

Other more local-scale results presented by the same team showed that surface-type erosion, or sheet erosion, which applies to all the surface considered, was the cause of almost all the soil losses affecting the western Sierra Madre. The proportion of fertile land lost by flooding-induced gully erosion was estimated at 2% of total erosion, even though a large amount of the material dragged down from the mountain slopes themselves were in fact transported through the gullies so formed. These original measurements suggest that, in this northern area of Mexico, it is the soils of all the drainage slopes that lose several millimetres every year. In this part of the country, with its steep slopes, this process was found to be the consequence of livestock’s trampling of vegetation combined with the sheer intensity of rainfall events. The intense grazing pressure exerted by cattle, which eat mainly grassy and herbaceous plants, means that the unpalatable species that the livestock leave alone no longer have any competition and eventually take over the whole of the space. This overgrazing therefore causes the grassland ecosystem to be replaced by thorn scrub and pine, less effective for holding in place the fine layer of fertile soil.

In the space of around ten years, pressure from ever-growing herds and tree-felling for timber have contributed greatly to changes in the landscape. In the western Sierra Madre, practically all the pasture land located at 500 to 2500 m altitude are already degraded. Yet paradoxically it was in the valley bottoms where there was least rainfall that sheet erosion was most intense. These zones were also the site of the most degraded pastures and where runoff was strongest.

These observations provide scientists with a better understanding of the functioning of soil and the erosion processes in regions like northern Mexico where it is becoming especially intense. This type of approach offers a better way of assessing soil degradation. It should in the long term offer easier identification of the places most vulnerable to erosion and runoff, a capability useful for devising control measures to limit certain detrimental practices such as tree clearance or over-intense grazing practices.

Grégory Fléchet - DIC

(1) These research studies were conducted jointly with the Mexican institutions: CENID RASPA (Centro Nacional de Investigación Disciplinaria en la Relación Agua Suelo Planta Atmósfera, and the research centre of INIFAP (Instituto Nacional de Investigación Forestal y Agro-Pecuaria) in Gomez Palacio (Durango State)

(2)In geology, a soil corresponds to the layer of fertile earth resulting from weathering of a surface rock under the influence of climate, vegetation or living organisms.

Grégory Fléchet | alfa
Further information:
http://www.ird.fr/us/actualites/fiches/2007/fas281.pdf

More articles from Ecology, The Environment and Conservation:

nachricht Value from wastewater
16.08.2017 | Hochschule Landshut

nachricht Species Richness – a false friend? Scientists want to improve biodiversity assessments
01.08.2017 | Carl von Ossietzky-Universität Oldenburg

All articles from Ecology, The Environment and Conservation >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Fizzy soda water could be key to clean manufacture of flat wonder material: Graphene

Whether you call it effervescent, fizzy, or sparkling, carbonated water is making a comeback as a beverage. Aside from quenching thirst, researchers at the University of Illinois at Urbana-Champaign have discovered a new use for these "bubbly" concoctions that will have major impact on the manufacturer of the world's thinnest, flattest, and one most useful materials -- graphene.

As graphene's popularity grows as an advanced "wonder" material, the speed and quality at which it can be manufactured will be paramount. With that in mind,...

Im Focus: Exotic quantum states made from light: Physicists create optical “wells” for a super-photon

Physicists at the University of Bonn have managed to create optical hollows and more complex patterns into which the light of a Bose-Einstein condensate flows. The creation of such highly low-loss structures for light is a prerequisite for complex light circuits, such as for quantum information processing for a new generation of computers. The researchers are now presenting their results in the journal Nature Photonics.

Light particles (photons) occur as tiny, indivisible portions. Many thousands of these light portions can be merged to form a single super-photon if they are...

Im Focus: Circular RNA linked to brain function

For the first time, scientists have shown that circular RNA is linked to brain function. When a RNA molecule called Cdr1as was deleted from the genome of mice, the animals had problems filtering out unnecessary information – like patients suffering from neuropsychiatric disorders.

While hundreds of circular RNAs (circRNAs) are abundant in mammalian brains, one big question has remained unanswered: What are they actually good for? In the...

Im Focus: RAVAN CubeSat measures Earth's outgoing energy

An experimental small satellite has successfully collected and delivered data on a key measurement for predicting changes in Earth's climate.

The Radiometer Assessment using Vertically Aligned Nanotubes (RAVAN) CubeSat was launched into low-Earth orbit on Nov. 11, 2016, in order to test new...

Im Focus: Scientists shine new light on the “other high temperature superconductor”

A study led by scientists of the Max Planck Institute for the Structure and Dynamics of Matter (MPSD) at the Center for Free-Electron Laser Science in Hamburg presents evidence of the coexistence of superconductivity and “charge-density-waves” in compounds of the poorly-studied family of bismuthates. This observation opens up new perspectives for a deeper understanding of the phenomenon of high-temperature superconductivity, a topic which is at the core of condensed matter research since more than 30 years. The paper by Nicoletti et al has been published in the PNAS.

Since the beginning of the 20th century, superconductivity had been observed in some metals at temperatures only a few degrees above the absolute zero (minus...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Call for Papers – ICNFT 2018, 5th International Conference on New Forming Technology

16.08.2017 | Event News

Sustainability is the business model of tomorrow

04.08.2017 | Event News

Clash of Realities 2017: Registration now open. International Conference at TH Köln

26.07.2017 | Event News

 
Latest News

A Map of the Cell’s Power Station

18.08.2017 | Life Sciences

Engineering team images tiny quasicrystals as they form

18.08.2017 | Physics and Astronomy

Researchers printed graphene-like materials with inkjet

18.08.2017 | Materials Sciences

VideoLinks
B2B-VideoLinks
More VideoLinks >>>