Choosing the “least expensive” healthy food options could cut dietary emissions by one-third, according to a new study.
In addition to the lower emissions, diets composed of low-cost, healthy foods would cost roughly one-third as much as a diet of the most-consumed foods in every country.
The study, published in Nature Food, compares prices and emissions associated with 440 local food products in 171 countries.
The researchers identify some food groups that are low in both cost and emissions, including legumes, nuts and seeds, as well as oils and fats.
Some of the most widely consumed foods – such as wheat, maize, white beans, apples, onions, carrots and small fish – also fall into this category, the study says.
One of the lead authors tells Carbon Brief that while food marketing has promoted the idea that eating environmentally friendly diets is “very fancy and expensive”, the study shows that such diets are achievable through cheap, everyday foods.
Meanwhile, a separate Nature Food study found that reforming the policies that reduce taxes on meat products in the EU could decrease food-related emissions by up to 5.7%.
Costs and emissions
The study defines a healthy diet using the “healthy diet basket” (HDB), which is a standard based on nutritional guidelines that includes a range of food groups with the needed nutrients to provide long-term health.
Using both data on locally available products and food-specific emissions databases, the authors estimate the costs and greenhouse gas emissions of 440 food products needed for healthy diets in 171 countries.
They examine three different healthy diets: one using the most-consumed food products, one using the least expensive food products and one using the lowest-emitting food products.
Each of these diets is constructed for each country, based on costs, emissions, availability and consumption patterns.
The researchers find that a healthy diet comprising the most-consumed foods within each country – such as beef, chicken, pork, milk, rice and tomatoes – emits an average of 2.44 kilograms of CO2-equivalent (kgCO2e) and costs $9.96 (£7.24) in 2021 prices, per person and per day.
However, they find that a healthy diet with the least-expensive locally available foods in each country – such as bananas, carrots, small fish, eggs, lentils, chicken and cassava – emits 1.65kgCO2e and costs $3.68 (£2.68). That is approximately one-third of the emissions and one-third of the cost of the most-consumed products diet.
In comparison, a healthy diet with the lowest-emissions products – such as oats, tuna, sardines and apples – would emit just 0.67kgCO2e, but would cost nearly double the least-expensive diet, at $6.95 (£5.05).
This reveals the tradeoffs of affordability and sustainability – and shows that the least-expensive foods tend to produce lower emissions, according to the study.
Dr Elena Martínez, a food-systems researcher at Tufts University and one of the lead authors of the study, tells Carbon Brief this is generally true because lower-cost food production tends to use fewer fossil fuels and require less land-use change, which also cuts emissions.
Ignacio Drake is coordinator of the fiscal and economic policies at Colansa, an organisation promoting healthy eating and sustainable food systems in Latin America and the Caribbean.
Drake, who was not involved in the study, tells Carbon Brief that the research is a “step further” than previous work on healthy diets. He adds that the study “integrates and consolidates” previous analyses done by other groups, such as the World Bank and the UN Food and Agriculture Organization.
Food group differences
The research looks at six food groups: animal-sourced foods, oils and fats, fruits, legumes (as well as nuts and seeds), vegetables and starchy staples.
Animal-sourced foods – such as meat and dairy – are typically the most-emitting, and most-expensive, food group.
Within this group, the study finds that beef has the highest costs and emissions, while small fish, such as sardines, have the lowest emissions. Milk and poultry are amongst the least-expensive products for a healthy diet.
Starchy staple products also contribute to high emissions too, adds the study, because they make up such a large portion of most people’s calories.
Emissions from fruits, vegetables, legumes and oil are lower than those from animal-derived foods.
The following chart shows the energy contributions (top) and related emissions (bottom) from six major food groups in the three diets modelled by the study: lowest-cost (left), lowest-emission (middle) and most-common (right) food items.
The six food groups examined in the study are shown in different colours: animal-sourced foods (red), legumes, nuts and seeds (blue), oils and fats (purple), vegetables (green), fruits (orange) and starchy staples (yellow). The size of each box represents the contribution of that food to the overall dietary energy (top) and greenhouse gas emissions (bottom) of each diet.
Prof William Masters, a professor at Tufts University and author on the study, tells Carbon Brief that balancing food groups is important for human health and the environment, but local context is also important. For example, he points out that in low-income countries, some people do not get enough animal-sourced foods.
For Drake, if there are foods with the same nutritional quality, but that are cheaper and produce fewer emissions, it is logical to think that the “cost-benefit ratio [of switching] is clear”.
Other studies and reports have also modelled healthy and sustainable diets and, although they do not exclude animal-sourced foods, they do limit their consumption.
A recent study estimated that a global food system transformation – including a diet known as the “planetary health diet”, based on cutting meat, dairy and sugar and increasing plant-based foods, along with other actions – can help limit global temperature rise to 1.85C by 2050.
The latest EAT-Lancet Commission report found that a global shift to healthier diets could cut non-CO2 emissions from agriculture, such as methane and nitrous oxide, by 15%. The report recommends increasing the production of fruit, vegetable and nuts by two-thirds, while reducing livestock meat production by one-third.
Dr Sonia Rodríguez, head of the department of food, culture and environment at Mexico’s National Institute of Public Health, says that unlike earlier studies, which project ideal scenarios, this new study also evaluates real scenarios and provides a “global view” of the costs and emissions of diets in various countries.
Increasing access
The study points out that as people’s incomes increase, their consumption of expensive foods also increases. However, it adds, some people with high income that can afford healthy diets often consume other types of foods, due to reasons such as preferences, time and cooking costs.
The study stresses that nearly one-third of the world’s population – about 2.6 billion people – cannot afford sufficient food products required for a healthy diet.
In low-income countries, primarily in sub-Saharan Africa and south Asia, 75% of the population cannot afford a healthy diet, says the study.
In middle-income countries, such as China, Brazil, Mexico and Russia, more than half of the population can afford such a diet.
To improve the consumption of healthy, sustainable and affordable foods, the authors recommend changes in food policy, increasing the availability of food at the local level and substituting highly emitting products.
Martínez also suggests implementing labelling systems with information on the environmental footprint and nutritional quality of foods. She adds:
“We need strategies beyond just reducing the cost of diets to get people to eat climate-friendly foods.”
Drake notes that there are public and financial policies that can help reduce the consumption of unhealthy and unsustainable foods, such as taxes on unhealthy foods and sugary drinks. This, he adds, would lead to better health outcomes for countries and free up public resources for implementing other policies, such as subsidies for producing healthy food.
Separately, another recent Nature Food study looks at taxes specifically on meat products, which are subject to reduced value-added tax (VAT) in 22 EU member states.
It finds that taxing meat at the standard VAT rate could decrease dietary-related greenhouse gases by 3.5-5.7%. Such a levy would also have positive outcomes for water and land use, as well as biodiversity loss, according to the study.
The post Adopting low-cost ‘healthy’ diets could cut food emissions by one-third appeared first on Carbon Brief.
Adopting low-cost ‘healthy’ diets could cut food emissions by one-third
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Drought and heatwaves occurring together – known as “compound” events – have “surged” across the world since the early 2000s, a new study shows.
Compound drought and heat events (CDHEs) can have devastating effects, creating the ideal conditions for intense wildfires, such as Australia’s “Black Summer” of 2019-20 where bushfires burned 24m hectares and killed 33 people.
The research, published in Science Advances, finds that the increase in CDHEs is predominantly being driven by events that start with a heatwave.
The global area affected by such “heatwave-led” compound events has more than doubled between 1980-2001 and 2002-23, the study says.
The rapid increase in these events over the last 23 years cannot be explained solely by global warming, the authors note.
Since the late 1990s, feedbacks between the land and the atmosphere have become stronger, making heatwaves more likely to trigger drought conditions, they explain.
One of the study authors tells Carbon Brief that societies must pay greater attention to compound events, which can “cause severe impacts on ecosystems, agriculture and society”.
Compound events
CDHEs are extreme weather events where drought and heatwave conditions occur simultaneously – or shortly after each other – in the same region.
These events are often triggered by large-scale weather patterns, such as “blocking” highs, which can produce “prolonged” hot and dry conditions, according to the study.
Prof Sang-Wook Yeh is one of the study authors and a professor at the Ewha Womans University in South Korea. He tells Carbon Brief:
“When heatwaves and droughts occur together, the two hazards reinforce each other through land-atmosphere interactions. This amplifies surface heating and soil moisture deficits, making compound events more intense and damaging than single hazards.”
CDHEs can begin with either a heatwave or a drought.
The sequence of these extremes is important, the study says, as they have different drivers and impacts.
For example, in a CDHE where the heatwave was the precursor, increased direct sunshine causes more moisture loss from soils and plants, leading to a drought.
Conversely, in an event where the drought was the precursor, the lack of soil moisture means that less of the sun’s energy goes into evaporation and more goes into warming the Earth’s surface. This produces favourable conditions for heatwaves.
The study shows that the majority of CDHEs globally start out as a drought.
In recent years, there has been increasing focus on these events due to the devastating impact they have on agriculture, ecosystems and public health.
In Russia in the summer of 2010, a compound drought-heatwave event – and the associated wildfires – caused the death of nearly 55,000 people, the study notes.
The record-breaking Pacific north-west “heat dome” in 2021 triggered extreme drought conditions that caused “significant declines” in wheat yields, as well as in barley, canola and fruit production in British Columbia and Alberta, Canada, says the study.
Increasing events
To assess how CDHEs are changing, the researchers use daily reanalysis data to identify droughts and heatwaves events. (Reanalysis data combines past observations with climate models to create a historical climate record.) Then, using an algorithm, they analyse how these events overlap in both time and space.
The study covers the period from 1980 to 2023 and the world’s land surface, excluding polar regions where CDHEs are rare.
The research finds that the area of land affected by CDHEs has “increased substantially” since the early 2000s.
Heatwave-led events have been the main contributor to this increase, the study says, with their spatial extent rising 110% between 1980-2001 and 2002-23, compared to a 59% increase for drought-led events.
The map below shows the global distribution of CDHEs over 1980-2023. The charts show the percentage of the land surface affected by a heatwave-led CDHE (red) or a drought-led CDHE (yellow) in a given year (left) and relative increase in each CDHE type (right).
The study finds that CDHEs have occurred most frequently in northern South America, the southern US, eastern Europe, central Africa and south Asia.
Threshold passed
The authors explain that the increase in heatwave-led CDHEs is related to rising global temperatures, but that this does not tell the whole story.
In the earlier 22-year period of 1980-2001, the study finds that the spatial extent of heatwave-led CDHEs rises by 1.6% per 1C of global temperature rise. For the more-recent period of 2022-23, this increases “nearly eightfold” to 13.1%.
The change suggests that the rapid increase in the heatwave-led CDHEs occurred after the global average temperature “surpasse[d] a certain temperature threshold”, the paper says.
This threshold is an absolute global average temperature of 14.3C, the authors estimate (based on an 11-year average), which the world passed around the year 2000.
Investigating the recent surge in heatwave-leading CDHEs further, the researchers find a “regime shift” in land-atmosphere dynamics “toward a persistently intensified state after the late 1990s”.
In other words, the way that drier soils drive higher surface temperatures, and vice versa, is becoming stronger, resulting in more heatwave-led compound events.
Daily data
The research has some advantages over other previous studies, Yeh says. For instance, the new work uses daily estimations of CDHEs, compared to monthly data used in past research. This is “important for capturing the detailed occurrence” of these events, says Yeh.
He adds that another advantage of their study is that it distinguishes the sequence of droughts and heatwaves, which allows them to “better understand the differences” in the characteristics of CDHEs.
Dr Meryem Tanarhte is a climate scientist at the University Hassan II in Morocco, and Dr Ruth Cerezo Mota is a climatologist and a researcher at the National Autonomous University of Mexico. Both scientists, who were not involved in the study, agree that the daily estimations give a clearer picture of how CDHEs are changing.
Cerezo-Mota adds that another major contribution of the study is its global focus. She tells Carbon Brief that in some regions, such as Mexico and Africa, there is a lack of studies on CDHEs:
“Not because the events do not occur, but perhaps because [these regions] do not have all the data or the expertise to do so.”
However, she notes that the reanalysis data used by the study does have limitations with how it represents rainfall in some parts of the world.
Compound impacts
The study notes that if CDHEs continue to intensify – particularly events where heatwaves are the precursors – they could drive declining crop productivity, increased wildfire frequency and severe public health crises.
These impacts could be “much more rapid and severe as global warming continues”, Yeh tells Carbon Brief.
Tanarhte notes that these events can be forecasted up to 10 days ahead in many regions. Furthermore, she says, the strongest impacts can be prevented “through preparedness and adaptation”, including through “water management for agriculture, heatwave mitigation measures and wildfire mitigation”.
The study recommends reassessing current risk management strategies for these compound events. It also suggests incorporating the sequences of drought and heatwaves into compound event analysis frameworks “to enhance climate risk management”.
Cerezo-Mota says that it is clear that the world needs to be prepared for the increased occurrence of these events. She tells Carbon Brief:
“These [risk assessments and strategies] need to be carried out at the local level to understand the complexities of each region.”
The post Heatwaves driving recent ‘surge’ in compound drought and heat extremes appeared first on Carbon Brief.
Heatwaves driving recent ‘surge’ in compound drought and heat extremes
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