We often picture climate change drying up rainforests, oceans and other hotbeds of biodiversity. But what happens to regions that are already dry? Far from barren, deserts and drylands sustain a surprising variety of animal species, as well as human life — but not for long, if global temperatures continue to rise. Climate change and human activity are disturbing these delicate ecosystems, and new research shows it could have serious environmental, human and economic consequences. But as we approach 2014 – the halfway point in the U.N.’s Decade for Deserts and the Fight against Desertification – desertification remains largely invisible in the conservation agenda. It get little press and is rarely addressed by policymakers.
Climate change-induced drought, overgrazing and unsustainable farming practices lead to a loss of vegetation, which in turn further parches arid lands by exposing infertile lower soil layers that are less able to support agriculture and wildlife — a process known as desertification . A U.N.-backed report released by the Economics of Land Degradation (ELD) in September found that up to one-fifth of drylands are degraded, resulting in estimated economic losses of about $40 billion per year.
STALLED DEVELOPMENT
Despite its low priority, desertification exacts a steep human cost. Drylands, which occupy roughly 40 percent of the Earth’s land area, are home to two billion people, mostly in developing African nations. According to the ELD report, annual global losses of arable land can reach 10 million hectares per year, an area roughly the size of Austria. Poor productivity in arid regions also makes them less attractive to investment, which excludes them from development.
FOOD INSECURITY
Although the poor suffer most from desertification, we may all end up feeling its impact. The decline in arable land renews concerns about the world’s ability to feed a booming population. The U.N.’s Food and Agriculture Organization predicts that the demand for food will increase 60 percent by 2050, which will require an additional 120 million hectares of agricultural land. That’s a farm the size of South Africa.
The good news? Adopting sustainable land management — such as crop rotation, which involves growing different crops in succession in the same field – could increase world crop supplies by an estimated 2.3 billion tons, worth $1.4 trillion. Managed grazing practices – such as letting livestock graze on only one portion of pasture while allowing others to recover – might also help, the report added.
Wildlife in these regions is also on the decline. Last Tuesday, the Wildlife Conservation Society and Zoological Society of London reported that half of the species historically found in the Sahara Desert are approaching extinction, most likely due to desertification and overhunting. Seven out of 14 species historically found in the Sahara, the world’s largest tropical desert, are regionally extinct or confined to 10 percent or less of their historical range. The lion, African wild dog and a type of antelope called the bubal hartebeest have vanished entirely from the region. Other species have fared only slightly better. Only the Nubian ibex still inhabits most of its historical range, but it’s still classified as vulnerable.
Violence and instability across the region contribute to a lack of studies, which makes it hard to pinpoint the exact cause of the wildlife decline, but desertification and overhunting are the most likely culprits, researchers say.
“The Sahara serves as an example of a wider historical neglect of deserts and the human communities who depend on them,” conservation biologist and study leader Sarah Durant said in a statement.
This may be our last opportunity to put deserts back on the radar. The longer we treat them as invsible, the more likely they actually will vanish – and the desert communities and ecosystems along with them.
The theme of this year’s Earth Day is “Planet vs. Plastics” – a theme chosen to raise awareness of the damage done by plastic to humans, animals and the planet and to promote policies aiming to reduce global plastic production by 60 percent by 2040.
As our chart shows, global plastics use has increased rapidly over the past few decades, growing 250 percent since 1990 to reach 460 million tonnes in 2019, according to the OECD’s Global Plastics Outlook, which projects another 67-percent increase in global plastics use by 2040 and for the world’s annual plastic use to exceed one billion tonnes by 2052. As our chart shows, packaging is the largest driver of global plastics use, which is why a rapid phasing out of all single use plastics by 2030 is one of the policy measures proposed under EARTHDAY.ORG’s 60X40 framework.
Other major applications of plastics include building and construction, transportation as well as textiles, with the fast fashion industry particularly guilty of adding to the world’s plastic footprint. “The fast fashion industry annually produces over 100 billion garments,” the Earth Day organizers write. “Overproduction and overconsumption have transformed the industry, leading to the disposability of fashion. People now buy 60 percent more clothing than 15 years ago, but each item is kept for only half as long.” Most importantly, the organization points out that 85 percent of disposed garments end up in landfills or incinerators, while just 1 percent are being recycled.
Felix Richter is a Data Journalist
This article was first published in the Statista.com.
Algeria’s Tassili N’Ajjer plateau is Africa’s largest national park. Among its vast sandstone formations is perhaps the world’s largest art museum. Over 15,000 etchings and paintings are exhibited there, some as much as 11,000 years old according to scientific dating techniques, representing a unique ethnological and climatological record of the region.
Curiously, however, these images do not depict the arid, barren landscape that is present in the Tassili N’Ajjer today. Instead, they portray a vibrant savannah inhabited by elephants, giraffes, rhinos and hippos. This rock art is an important record of the past environmental conditions that prevailed in the Sahara, the world’s largest hot desert.
These images depict a period approximately 6,000-11,000 years ago called the Green Sahara or North African Humid Period. There is widespread climatological evidence that during this period the Sahara supported wooded savannah ecosystems and numerous rivers and lakes in what are now Libya, Niger, Chad and Mali.
This greening of the Sahara didn’t happen once. Using marine and lake sediments, scientists have identified over 230 of these greenings occurring about every 21,000 years over the past eight million years. These greening events provided vegetated corridors which influenced species’ distribution and evolution, including the out-of-Africa migrations of ancient humans.
These dramatic greenings would have required a large-scale reorganisation of the atmospheric system to bring rains to this hyper arid region. But most climate models haven’t been able to simulate how dramatic these events were.
As a team of climate modellers and anthropologists, we have overcome this obstacle. We developed a climate model that more accurately simulates atmospheric circulation over the Sahara and the impacts of vegetation on rainfall.
We identified why north Africa greened approximately every 21,000 years over the past eight million years. It was caused by changes in the Earth’s orbital precession – the slight wobbling of the planet while rotating. This moves the Northern Hemisphere closer to the sun during the summer months.
This caused warmer summers in the Northern Hemisphere, and warmer air is able to hold more moisture. This intensified the strength of the West African Monsoon system and shifted the African rainbelt northwards. This increased Saharan rainfall, resulting in the spread of savannah and wooded grassland across the desert from the tropics to the Mediterranean, providing a vast habitat for plants and animals.
Our results demonstrate the sensitivity of the Sahara Desert to changes in past climate. They explain how this sensitivity affects rainfall across north Africa. This is important for understanding the implications of present-day climate change (driven by human activities). Warmer temperatures in the future may also enhance monsoon strength, with both local and global impacts.
Earth’s changing orbit
The fact that the wetter periods in north Africa have recurred every 21,000 years or so is a big clue about what causes them: variations in Earth’s orbit. Due to gravitational influences from the moon and other planets in our solar system, the orbit of the Earth around the sun is not constant. It has cyclic variations on multi-thousand year timescales. These orbital cycles are termed Milankovitch cycles; they influence the amount of energy the Earth receives from the sun.
On 100,000-year cycles, the shape of Earth’s orbit (or eccentricity) shifts between circular and oval, and on 41,000 year cycles the tilt of Earth’s axis varies (termed obliquity). Eccentricity and obliquity cycles are responsible for driving the ice ages of the past 2.4 million years.
The third Milankovitch cycle is precession. This concerns Earth’s wobble on its axis, which varies on a 21,000 year timescale. The similarity between the precession cycle and the timing of the humid periods indicates that precession is their dominant driver. Precession influences seasonal contrasts, increasing them in one hemisphere and reducing them in another. During warmer Northern Hemisphere summers, a consequent increase in north African summer rainfall would have initiated a humid phase, resulting in the spread of vegetation across the region.
Eccentricity and the ice sheets
In our study we also identified that the humid periods did not occur during the ice ages, when large glacial ice sheets covered much of the polar regions. This is because these vast ice sheets cooled the atmosphere. The cooling countered the influence of precession and suppressed the expansion of the African monsoon system.
The ice ages are driven by the eccentricity cycle, which determines how circular Earth’s orbit is around the sun. So our findings show that eccentricity indirectly influences the magnitude of the humid periods via its influence on the ice sheets. This highlights, for the first time, a major connection between these distant high latitude and tropical regions.
The Sahara acts as a gate. It controls the dispersal of species between north and sub-Saharan Africa, and in and out of the continent. The gate was open when the Sahara was green and closed when deserts prevailed. Our results reveal the sensitivity of this gate to Earth’s orbit around the sun. They also show that high latitude ice sheets may have restricted the dispersal of species during the glacial periods of the last 800,000 years.
Our ability to model the African humid periods helps us understand the alternation of humid and arid phases. This had major consequences for the dispersal and evolution of species, including humans, within and out of Africa. Furthermore, it provides a tool for understanding future greening in response to climate change and its environmental impact.
Refined models may, in the future, be able to identify how climate warming will influence rainfall and vegetation in the Sahara region, and the wider implications for society.
Edward Armstrong is a postdoctoral research fellow, University of Helsinki
A new draft text on global stocktake has been published at the UN climate summit, COP28 UAE, on Wednesday morning. While the draft text does not contain the words “phase out”, it includes reference to transitioning away from all fossil fuels to enable the world to reach net zero by 2050.
The text published by the UN’s climate body calls on parties to accelerate and substantially reduce non-carbon dioxide emissions worldwide with a focus on reducing methane emissions by 2030. “We all want to get the most ambitious outcome possible,” Majid Al Suwaidi, COP28 Director-General, said on Tuesday.
The text, published early Wednesday, does not specifically refer to oil, but mentions the need to ‘phase-down’ coal. It says that it recognises the need for ‘deep, rapid and sustained reductions in greenhouse gas emissions in line with 1.5C pathways and calls on Parties to contribute to global efforts.
Among those efforts it recognises the need to triple renewable energy capacity by 2030 and doubling the annual rate of energy efficiency improvements by the same date. It also recognises the need to accelerate the phase-down of coal and accelerate towards net zero energy systems, utilising zero or low carbon fuels by mid century.
While the document does not mention oil or combustion engines, it does recognises the need for accelerating the reduction of emissions from road transport on a range of pathways, including through development of infrastructure and rapid deployment of zero and low-emission vehicles. It also recognises the need to phase out inefficient fossil fuel subsidies that do not address energy poverty or just transitions, as soon as possible.
Finance specifics
On the subject of finance, the document said developed countries should continue to take the lead in mobilising climate finance from a wide variety of sources, instruments and channels, noting the significant role of public funds, through a variety of actions, including supporting country-driven strategies, and taking into account the needs and priorities of developing countries.
Such mobilisation of climate finance should represent a progression beyond previous efforts, the text said. It may provide small comfort to campaigners from developing countries who implored Parties to begin the phase out of fossil fuels and provide vastly improved access to funding for renewables.
The document highlights the persistent gap and challenges in technology development and transfer and the uneven pace of adoption of climate technologies around the world.
It further urges Parties to address these barriers and strengthen cooperative action, including with non-Party stakeholders, particularly with the private sector, to rapidly scale up the deployment of existing technologies, the fostering of innovation and the development and transfer of new technologies.
It also emphasizes the ongoing challenges faced by many developing country Parties in accessing climate finance and encourages further efforts, including by the operating entities of the Financial Mechanism, to simplify access to such finance, in particular for those developing country Parties that have significant capacity constraints, such as the least developed countries and small island developing States.
