Tag Archives: land use

We’ve changed a third of the Earth’s land surface in less than 60 years

A third of the global land surface, or 43 million squared kilometers, has been subject to change from 1960 to 2019, driven by an expansion in agriculture and cattle ranching, a new study shows. This means that on average a land area of about twice the size of Germany (720,000 squared kilometers) has been altered every year since 1960.

Image credit: CIFOR

“Land-use change” refers to ways in which humans alter the natural landscape. This can be permanent destruction, such as urban expansion, or just temporary. Some changes, such as forest restoration or regeneration, may attempt to repair previous damage. Overall, it’s a widespread phenomenon, previous studies have shown. But we weren’t expecting it to be this widespread.

Land use is usually measured by high-resolution satellite imagery and by large-scale statistical surveys. But each method has its own shortcomings when assessing land-use change. Satellites can capture land use in high detail, but their records only extend back a few decades, while statistical methods go further back in time but at a worse resolution.

Little work has been done to combine both approaches – until now. Karina Winkler, a physical geographer at Wageningen University & Research in the Netherlands, and her colleagues brought together more than 20 satellite land-use products and long-term surveys. The resulting dataset captures changes in land use with a 1km resolution.

But not all land-use change is permanent. So instead of looking at “net” changes that only capture the overall transformation of an area, the dataset captures places where land use has changed multiple times, such as rotation between cropland and pasture. When this is added, the extent of land-use change is really massive.

The map below, done by the researchers shows where both single-change (yellow shading) and multiple-change (red) events are occurring around the world. Instances of multiple-change events are dominant across Europe, India, and the US, while single-change events are widespread across South America, China, and south-east Asia.

Image credit: The researchers

Land-use change

For their study, Winkler and her team established six categories of land use, following the definitions used by the Food and Agriculture Organization (FAO): urban areas, cropland, pasture, unmanaged grassland, forest, and sparsely vegetated land. Notable patterns jump out when looking at what types of change are occurring where.

For example, about half of the single-change events (or nearly 20% of the total changes) happen because of agricultural expansion, such as deforestation. And 86% of the multiple-change events are agriculture-related, predominantly happening in the global north and select rapidly growing economies.

Averaged globally, land-use change steadily increased for nearly half a century. But, in 2005, there was a “rather abrupt change” in this trend and land-use change began decelerating worldwide, the authors found. This is most evident in Africa, South America, and regions of Subtropics and Tropics and linked to market developments.

The charts below show the differences in land-use change rates in six geographical regions, as well as the worldwide average. The global rates of change are defined by an acceleration period from 1960 to the early 2000s, followed by deceleration since about 2005. Land-use change is responsive to “socio-economic developments,” the authors write.

Image credit: The researchers

Almost one-quarter of total human-caused greenhouse gas emissions between 2007 and 2016 were due to agriculture, forestry, and other land use, according to the Intergovernmental Panel on Climate Change (IPCC). This falls just behind electricity and heat production as the world’s second-largest contributor to global emissions.

But if conserved properly land can actually help bring down emissions, acting as a sink of greenhouse gases – for example with the carbon absorbed by the forests. The balance of sources and sinks through land-use change, the IPCC says, is a “key source of uncertainty” in considering the future of the land carbon cycle.

The study was published in the journal Nature Communications.

It’s not just oil and coal. We need to tackle agriculture emissions too, study shows

A thorough inventory of the sector’s emissions underlined just how much agriculture contributes to our greenhouse gas emissions. If we want to avoid catastrophic damage, we’d be wise to address this, researchers say.

Image credit: Flickr / StateOfIsrael

Land-use and agriculture emissions are on the rise in most countries and this could cause the world to fail its climate targets, which could cause devastating damage for the entire planet.

Historically, human land use has affected the environment in multiple ways: it transformed and fragmented ecosystems, degraded biodiversity, disrupted carbon and nitrogen cycles, and added emissions to the atmosphere. But in contrast to fossil-fuels, trends and drivers of emissions from land-use change haven’t been analyzed as thoroughly.

The first problem is complexity. Compared to fossil fuels, land-use emissions are more difficult to assess. They are spatially diffuse, temporally distributed (for example, emissions from a deforested area may occur over many years), and require substantially more data and disciplinary knowledge to estimate. They are also comparatively more difficult to avoid.

A group of researchers from the University of California carried out a country-level analysis of trends in global land-use emissions in 1961–2017 and their demographic, economic, and technical drivers. They used annual time-series data on population, crop and livestock production, land area harvested, and agricultural emissions.

“We estimated and attributed global land-use emissions among 229 countries and areas and 169 agricultural products,” lead author Chaopeng Hong, said in a statement. “We looked into the processes responsible for higher or lower emissions and paid particularly close attention to trends in net CO2 emitted from changes in land use.”

Despite steady increases in population and agricultural production per capita, as well as smaller increases in emissions per land area used, land-use emissions relatively constant at about 11 gigatons CO2-equivalent until 2001, the study showed. This is mainly due to decreases in land required per unit of agricultural production.

But it all changed after 2001. Driven by rising emissions per land area, emissions increased by 2.4 gigatons CO2-equivalent per decade to 14.6 gigatons CO2-equivalent in 2017, the researchers found. This represents about 25% of total anthropogenic emissions, making agriculture a large contributor to global emissions, contributing to about a quarter of our total emissions.

Latin America, Southeast Asia, and sub-Saharan Africa are the three highest-emitting regions, accounting for 53% of global land-use emissions and more than two-thirds of global emissions growth over the period from 1961 to 2017. This is linked to cropland expansion and concomitant spikes in the emissions intensity of land use.

In the case of Latin America, increases in emissions after the year 2000 reversed earlier long-term declines; emissions in this region reached roughly 75% of 1961 levels in the 1990s. By contrast, emissions in Southeast Asia and sub-Saharan Africa have trended upwards throughout most of that period, driven by significant growth in production.

A meaty problem

The researchers also looked at different food groups and found some striking differences. Emissions per calorie of beef and other meat are 30 times greater than the average intensity of other products. Although these red meats supply just 1% of total calories produced worldwide, they account for 25% of total land-use emissions.

Between 1961 and 2017, beef production increased much less (+144%) than chicken and pork production (483%), reflecting a widespread shift in the type of meat consumed, which reduced per capita meat emissions in 2017 by 44%. This has caused a 14% decline in per capita land-use emissions in the period included in the study.

“While the situation in low-income countries is critical, mitigation opportunities in these places are large and clear,” senior author Steve Davis said in a statement. “Improving yields on already cultivated land can avoid clearing more carbon-dense forests for cultivation of soybeans, rice, maize and palm oil, thereby drastically reducing land-use emissions in these countries.”

The researchers argued countries can tackle the emissions of the agricultural sector by reducing food waste, improving the quality of the soil, better manage livestock waste and use more efficient tilling and harvesting methods. At the same time, dietary changes could also make a big difference, as highlighted in previous studies.

Recent research has also demonstrated some promising mitigation options, they added. For example, rice cultivars and non-continuous rice-paddy flooding practices may achieve substantial reductions in CH4 while also increasing yields, and dietary supplements for cattle have reduced methane emissions up to 95% in pilot studies.

The study was published in the journal Nature.

Dry cat- and dog-food production uses an area twice the size of the UK

The world’s pets eat a surprising amount of food, according to a new study. It reports that the dry food used to feed cats and dogs worldwide takes an area twice as large as the UK to grow every year.

Image via Pixabay.

Where would we be without our pets? Arguably, life wouldn’t be quite as enjoyable. But at the same time, we’d also save up on quite a lot of greenhouse gas emissions — more than are released by countries such as the Philippines. The findings come from a new study that looked at the global environmental impacts of the pet food industry.

Feeding fur babies

Enough people around the world now have pets that we need to accurately assess their environmental impact if we want to reach our climate targets, the team explains. The production of dry food intended for our pets especially needs to be analyzed, they add.

For the study, the researchers looked at the main ingredients used in over 280 types of dry food available in Europe and the US. These areas account for around two-thirds of the global sales of dry pet food.

Around half of the ingredients used are based on plant crops, mainly maize, rice, and wheat. The other half is made of a large selection of animal and fish products. From these figures, the authors estimate that dry dog and cat food production takes around 49 million hectares of agricultural land, which is roughly twice the size of the United Kingdom. Dry cat- and dog- food accounts for around 95% of all pet food production, even when accounting for the use of byproducts in pet foods.

As far as greenhouse gas emissions are concerned, this would account for roughly 106 million tons of CO2 per year. A country producing the same levels would be the world’s sixtieth highest emitter, the team explains.

The team says their findings should be factored into our climate estimations to better inform our actions. Furthermore, they show that the industry should be considered alongside other drivers of biodiversity loss such as agriculture and deforestation.

The paper “The global environmental paw print of pet food” has been published in the journal Global Environmental Change.

The way humans modify environments makes them more likely to cause outbreaks

The transformation of natural landscapes into farmland and cities is favoring animals such as bats, the possible source of the novel coronavirus, to carry more diseases. This is the main finding of a new study found which looked at how ecosystems change as people expand on them.

Credit Flickr Wagner Cassimiro (CC BY 2.0)

A group of researchers, led by the Center for Biodiversity at the University of London, looked at data from 6,801 ecological communities from six continents. They found that animals known to carry pathogens that can infect humans were more common in landscapes intensively used by people.

The evidence was obtained from a dataset of 184 studies, which incorporate almost 7,000 species, 376 of which carry human-shared pathogens. The findings show that we have to alter the way we use the land across the world so as to reduce the risk of infectious diseases in the future, the researchers argued.

Many factors are involved in a disease spillover, which is when a pathogen moves from an animal into humans, causing disease outbreaks, which can later become a pandemic. Close contact with wild animals through trade or habitat loss, for example, increases the risk of new diseases.

Bats have been mentioned as the possible origin of the novel coronavirus, with other animals also playing a role in the spillover to humans. Wild animals that face possible extinction due to human exploitation were found to carry over twice as many viruses that can lead to human disease.

“The way humans change landscapes across the world, from natural forest to farmland, for example, has consistent impacts on many wild animal species, causing some to decline while some others persist or increase,” said lead-author Rory Gibb in a press release. “Animals that remain in more human-dominated environments are those that are more likely to carry infectious diseases.”

The study found that species that host zoonotic pathogens, those which can move from animals to humans, accounted for a higher proportion of the animal species found in environments that have been altered by humans, compared with more wild habitats.

The same finding was replicated in animals that usually carry more pathogens of any kind, whether they affect humans or not. This shows, according to the researchers, that similar factors could be influencing whether a species can tolerate humans and how likely it is to carry zoonotic diseases.

“Other studies have found that outbreaks of emerging zoonotic infectious diseases appear to be increasingly common — our findings may help to explain that pattern, by clarifying the underlying ecological change processes that are interacting to drive infection risks,” said co-lead author Dr. David Redding in a press release.

The study was published in the journal Nature.