Cattle grazing on pastures that were on an ecological knife edge and desertification.

 

Photo credit: International Business Times

The Sahara desert was lush and green 10,000 years ago. Within a few thousand years it became barren. Humans are now thought to have pushed it over the edge – Wonker / Flickr

Did humans turn the Sahara from a lush, green landscape into a desert?

Cattle grazing on pastures that were on an ecological knife edge could have pushed the Sahara onto the path of desertification.

martha-henriques

The Sahara used to be a fertile landscape with lush vegetation thousands of years ago, but something killed that landscape, leaving only desert behind. Neolithic humans may have played a role in pushing it over the edge of an ecological tipping point, an archaeological study finds.

The Sahara used to be a lush, green environment as little as 6,000 years ago, when humans grazed cattle on green pastures. Theories for what turned the Sahara into a desert in a period of just a few thousand years include shifting circulation in the tropical atmosphereand changes in the Earth’s tilt.

Archaeological evidence now suggests that Neolithic humans who grazed cattle on the Saharan pastures played a role as well. These pastoral communities pushed the delicate ecosystem past a tipping point that led to widespread desertification, according to a paper published in the journal Frontiers in Earth Science.

Study author David Wright of Seoul National University, South Korea, mapped the spread of scrub vegetation, which is a precursor to full desertification, and evidence of Neolithic cattle grazing. As more and more vegetation was removed from the land, the albedo – or amount of light reflected from the ground – increased, changing the atmospheric conditions over the Sahara. This in turn made monsoon rains less frequent.

About 8,000 years ago, cattle-grazing communities originated near the River Nile and began gradually to spread to the west of the continent. Rather than the spread of the communities happening in response to desertification and loss of vegetation, the humans could have been actively driving the desertification, Wright suggests.

Read the full story: International Business Times

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Grazers hasten ecosystem collapse from drought

 

 

Pressures from grazers hastens ecosystem collapse from drought

Experiments show grazing pressures compound drought stress, delay recovery

Date:
January 11, 2017
Source:
Duke University
Summary:
Ecosystem collapse from extreme drought can be significantly hastened by pressures placed on drought-weakened vegetation by grazers and fungal pathogens, a new study finds. The study’s experimental evidence shows that the natural enemies of plants play a major role in lowering resilience to drought and preventing recovery afterward. The finding may be applicable to a wide range of ecosystems now threatened by climate-intensified drought, including marshes, mangroves, forests and grasslands.

 

A new study by scientists at Duke University and Beijing Normal University may hold the answer why.

The researchers found that these tipping points can happen much sooner than current models predict because of the added pressures placed on drought-weakened plants by grazing animals and fungal pathogens.

“Our work provides the first real-world experimental evidence that these natural enemies of plants can play a dramatic role in lowering ecosystems’ tipping point by killing drought-weakened vegetation and preventing plants from recovering,” said Brian R. Silliman, Rachel Carson Associate Professor of Marine Conservation Biology at Duke’s Nicholas School of the Environment.

Ecologists have long known that drought can stimulate this type of attack on plants, he said, but they mostly discounted it as a secondary stress and not a main cause of ecosystem collapse.

“What we found is the opposite,” Silliman said. “Grazers have a strong compounding effect. This means these ecosystems are far more vulnerable to drought than the current models predict. With grazers present, they can handle much less drought stress.”

Read the full story: Science Daily

Protecting the environment, empowering people(IFAD)

 

 

https://www.ifad.org/documents/10180/e036916a-9d15-463f-8952-56d1566d7ac8

The Drylands Advantage

Protecting the environment, empowering people 

“Recognition of the true value of ecosystem services, and of the opportunities they offer, will enable better planning and realization of the full economic potential of dryland ecosystems, rebutting the common perception that drylands are ‘economic wastelands’” (IUCN, 2009).

Table of Contents

Acronyms 4

Introduction 5

China: Boosting biodiversity for benefits to people and the environment 9

Jordan: Sustainable land management 15

Nicaragua: Nutrition security in the Dry Corridor in the face of El Niño 21

Senegal: What a little freshwater can do 27

Swaziland: Grass-roots governance beats overgrazing and gully erosion 32

Conclusions and next steps 37

References and resources consulted 39

L’utilisation des ressources naturelles au Sahel et en Afrique de l’Ouest

 

 

Conventions locales de gestion des ressources naturelles: schema pastoral au sud du Mali

by

En Afrique de l’Ouest, comme dans la plupart des pays d’Afrique Sub-Sahélienne, les ressources naturelles constituent la base de la vie quotidienne des hommes, particulièrement pour les pauvres qui dans la majorité des cas vivent dans le milieu rural où leur moyens de subsistances dépendent presque exclusivement des activités agricoles et de l’élevage.

La production agricole et l’élevage caractérise essentiellement l’économie de la région et se situe au cœur de l’utilisation des ressources naturelles au Sahel et en Afrique de l’Ouest. De nombreux facteurs, tels que l’augmentation constante de la population et l’accroissement des troupeaux, ont pour conséquence l’apparition d’une pression croissante sur ces ressources.

Cette vidéo met en évidence une tentative réussie par ILRI et AMEDD pour arrêter ce problème dans le sud du Mali.

Read the full story: Africa Rising

Climate, desertification, drought, rangeland management and overgrazing.

 

 

Rangeland management and climate hazards in drylands: dust storms, desertification and the overgrazing debate

by Nick Middleton

in Natural Hazards (2016). – doi:10.1007/s11069-016-2592-6

http://link.springer.com/article/10.1007/s11069-016-2592-6

Abstract

This paper examines the theory and supporting evidence for links between desertification, drought and dust storms with a particular focus on studies undertaken in and around the Gobi Desert.

Overgrazing of rangeland by pastoralists has been the most commonly cited cause of desertification in global drylands for more than 30 years, but the evidence supporting this link is not always convincing. Nonetheless, overgrazing, desertification and dust storms are frequently connected, regardless.

Drought is another well-known and important driver of vegetation cover change. Distinguishing between vegetation cover adversely affected by drought and that reduced by grazing is imperative for policy makers because identifying the incorrect driver of vegetation change risks the development of inappropriate policy.

Open Access Original Paper

DOI: 10.1007/s11069-016-2592-6

African dairy and “wonder grass” repatriated from Brazil

 

 

Brachiaria: The ‘wonder grass’ that could transform African dairy

Desertification, overgrazing and conflicts

Photo credit: Ecologist

The edge of an experimental sheep grazing exclusion zone (to the right) within Al Talila Reserve, Palmyra, photographed in March 2008 in the midst of an intense drought period. Sheep quasi uncontrolled grazing was allowed to the left of the fence. Grazing of reintroduced native antelopes at low densities had been allowed within the exclusion zone for a period of 10 years. Photo: Gianluca Serra.

Over-grazing and desertification in the Syrian steppe are the root causes of war

by Gianluca Serra

Civil war in Syria is the result of the desertification of the ecologically fragile Syrian steppe, writes Gianluca Serra – a process that began in 1958 when the former Bedouin commons were opened up to unrestricted grazing. That led to a wider ecological, hydrological and agricultural collapse, and then to a ‘rural intifada’ of farmers and nomads no longer able to support themselves.

———

A major role in this unfolding disaster was played by affluent urban investors who threw thousands of livestock into the steppe turning the grazing into a large-scale, totally unsustainable, industrial practice.