GHG Emissions and Agriculture

In a previous post we touched on the livestock sector's impact on greenhouse gas (GHG) emissions. Today, let's examine GHG emissions from the agricultural sector as a whole.

Emissions from agriculture occur in the form of carbon dioxide (CO2), methane (CH4), and nitrous oxide (N2O). CH4 and N2O are the most important sources of GHG emissions from agriculture, the agricultural sector contributing over 50% of the total amount anthropogenic emissions of these gases (Cole et al., 1997). Between 1990 and 2005, agricultural emissions of CH4 and N2O increased by 17%, equal to a an average annual emission rate of increase of approximately 60 megatonnes of CO2 equivalent (MtCO2-eq) per year (IPCC, 2007).

Agricultural fields in Brazil as seen from space (source: the Guardian)

Agricultural lands occupy approximately 40-50% of the Earth's land surface (IPCC, 2007), and can be clearly seen from space (e.g. above photo). Food systems today are so important that they contribute between 19 and 29% of the world's human-induced GHG emissions. Together, agriculture and forestry account for as much as one third of global GHG emissions (CGIAR, 2012). In 2008, approximately 9,800-16,900 MtCO2-eq were released from agricultural practices, agricultural production (including land cover change) comprising 80 to 86% of all food system emissions (Vermeulen, 2012).

Global agricultural emissions (CGIAR, 2013)

Various stages in the food production system are responsible for GHG emissions, as can be seen from the diagram above. The main three stages in the production of food include preproduction, production, and postproduction. By and large, the production stage which includes both direct and indirect emissions from agriculture contributes the largest portion of emissions. Within these stages of the food chain, regional variations exists with high-income countries contributing most to the postproduction stage (Vermeulen, 2012). 

Thornton (2012) argues that the effects of climate change will greatly affect the agricultural sector, and examines 22 common agricultural commodities' responses in the face of climate change. He states that "the world's agricultural system faces an uphill struggle", and that it will become a great challenge to feed global populations (as we saw with Foley, 2009). He also finds that the production of the most common commodity crops (wheat, maize, and rice) will be challenged by new weather patterns, as will the raising of livestock and catching of fish (two of the more common sources of protein). The Telegraph recently reported on the fact that the UK is now an importer of wheat because of large swings in weather conditions, exemplifying Thornton's (2012) findings (you can read the article here).

The UK was forced to switch from being an exporter of wheat to an
importer in 2013 (from the Telegraph)

At this point in our examination of current food systems, I'd like to take a little journey backwards in time. Remember when we talked about the origins of agriculture in November? We saw that the advent of agriculture about 10,000 years ago greatly altered human societies, and also the environment. What we didn't talk about was the early anthropogenic hypothesis, proposed by Ruddiman in 2003. Contrary to the popular notion that the Anthropocene began 150 to 200 years ago, altering the climate system by inputting CO2 and CH4 at industsrial rates, Ruddiman suggests that this transition in fact occurred thousands of years ago when agriculture was born. His three main arguments are that a) CO2 and CH4 concentrations anomalously began to increase 8,000 and 5,000 years ago, respectively; b) published explanations exist for mid- to late-Holocene gas increases which reject natural forcing; and c) wide arrays of archaeological, cultural, historical, and geologic evidence are available which point to anthropogenic impacts from early agriculture (in Eurasia in particular). Ruddiman's hypothesis is often criticised (see Ruddiman, 2007), but I thought it was worth mentioning and this post seemed like a good venue.

Regardless of when agriculture began to impact the climate system, it is clear that global food production is greatly contributing to climate change by inputting large amounts of GHGs into the atmosphere. The great challenge will be to produce enough food to feed the growing world, but at what cost? How will we manage to do so without imposing great climate change threats? If you're interested in mitigation strategies, you can read about it in chapter 8.4 of the IPCC's Fourth Assessment Report (AR4).

Thanks for reading, and have a Happy New Year!

Indigenous Fruits and Vegetables

Today's post is a quick little aside before we go on to explore GHG emissions from the agricultural sector as a whole later on in the week...

I was leisurely browsing the online world of food news this afternoon and came across this interesting article in the Guardian. The title, Healthy eating: nutritious indigenous foods you may never have heard of particularly caught my eye given the festive holiday season. After having eaten my fair share of sweets and decadent foods over the past week (and surely for the next week to come), I tend to get overly enthusiastic when I see articles with the word 'healthy' in their titles! 

Perinaldo artichokes (source: the Guardian)

The article describes a list of indigenous fruits and vegetables created by Food Tank: The Food ThinkTank that could present healthier alternatives to modern-day staples. The rationale behind the creation of the list is that the Western diet, which is rich in refined sugars, fats, processed grain and meat has taken over the world over the past three decades (e.g. Bonhommeau et al., 2013). This dietary shift has been linked with increased chronic disease incidence, including obesity and cardiovascular disease (Cordain, 2005). Organisations, such as the World Vegetable Center, are working to catalogue these indigenous foods, because many have been replaced and even lost as traditional diets are being replaced by Western diets. 

Amaranth (source: the Guardian)

The list includes some well known indigenous fruits and vegetables such as amaranth and argan (Africa), artichokes (Europe), okra, mungbean and lemongrass (Asia), and apples (Americas), as well as many others which I'd never heard of before (such as papalo from the Americas, which has a skunk-like smell and is known to regulate blood pressure and relieve stomach disorders).

Given that we recently touched on the Western diet when we examined the livestock sector, I thought that sharing this article would be a nice little break from all the hard-hitting environmental facts surrounding our food system. I'll be back to discuss the very imposing issue of GHG emissions from agriculture in a few days' time, so do check back soon.

For those of you that have come to study in the UK from abroad, are there any healthy traditional foods that are being replaced due to the emergence of a Western diet? I can't think of any examples from Canada off the top of my head, but I'll share in the comments if I come up with anything.

Thanks for reading!

The Other Inconvenient Truth

While researching the environmental impacts of increased meat consumption, I came across an excellent TED Talk by Jonathan Foley titled The Other Inconvenient Truth. He describes the current state of the food system and identifies the need for future solutions so that we can feed 9 billion people by 2040. He covers some examples of the environmental impacts of  the modern agricultural system, including the drying of the Aral Sea and rainforest degradation in South America. His talk provides a really nice review of some of the information covered in Are Humans Becoming More Carnivorous? as well as a nice segue into some of the future topics that we'll be exploring here.

If you have twenty minutes to spare, you can check out his talk below.

If not, here's the short and compelling clip that Jonathan shows at the end of his talk.

Thanks for reading!

Are Humans Becoming More Carnivorous? Environmental Impacts

In the previous post, we examined a new study by Bonhommeau et al. (2013) which revealed that global meat consumption has increased over the past five decades. How does an increase in meat consumption affect the environment?

Cows (photo from Living Green Magazine)

The livestock sector lies within the top two or three of the most important contributors to environmental issues, both locally and globally. Despite not being a major global economic player, the livestock sector is beneficial and crucial to society, employing and feeding growing global populations (Steinfeld et al., 2006; Herrero et al., 2009). Livestock agriculture contributes to environmental problems such as land degradation, land use change, climate change and greenhouse gas emissions, water shortage and pollution, nutrient excretion, loss of biodiversity, and competition for human food (Steinfeld et al., 2006; Janzen, 2011). These environmental impacts are driven by growing stresses on global human populations, namely the those of food, water, and energy security, biogeochemical interferences, and habitat (Janzen, 2011).

Let's now examine some of these impacts in a bit more detail. Many of the other impacts mentioned above will be the topics of future posts.

Land Use Change and Degradation

Land use refers to the ways in which land is used for human means. It is "characterised by the arrangements, activities and inputs that people undertake in a certain land cover type to produce change, or maintain it" (FAO, 2013). Land degradation refers to the reduction of resources as a result of processes which act on the land, including soil erosion, deterioration of the properties of the soil, and loss of natural vegetation (Steinfeld et al., 2006).

Deforestation for agriculture in Brazil's Pantanal wetland 
(from JNCC, 2013)

Livestock now represents the largest portion of human land use forms, affecting ecosystems around the world (Janzen, 2011). An example of environmental problems brought on by land use change for agriculture is the degradation of tropical rainforests, such as the Amazon. Two main phenomena are related to deforestation as a result of intensive raising of livestock, the first being the direct conversion of forest to pasture land and the second being the clearing of forest for crop growth to feed livestock (Herrero et al., 2009). Approximately 20-30% of the Earth's land surfaces are used for grazing, while approximately one third of cultivated land area is used to feed livestock (Janzen, 2011). 

GHG Emissions & Climate Change

Climate change is possibly the most pressing environmental challenge that has faced the planet. According to the IPCC (2013), the main authority on climate change, the "warming of the climate system is unequivocal, and since the 1950s, many of the observed changes are unprecedented over decades to millennia". This warming can be seen in the atmosphere, the ocean, the cryosphere, in sea level, and in carbon and biogeochemical cycles. The largest contributor to total radiative forcing is caused by the increases in anthropogenic GHGs, such as CO2, since 1750.

Disintegrating iceberg near West Greenland
(from The Guardian)

Animal agriculture produces GHG emissions in the form of CH4 from enteric fermentation, N2O from fertiliser use, CH4 and N2O from manure management practices, and CO2 from from fossil fuel and energy use (O'Mara, 2011) and land use and its changes (Herrero et al., 2009). Livestock induced emissions account for 2.4 billion tonnes of CO2 per year, and on a life cycle analysis basis, they contribute up to 18% of global GHG emissions (Steinfeld et al., 2006). 

Water Shortage and Pollution

Water is essential for life. Only 3% of the water on Earth is fresh, and surface water only accounts for 0.3% of the total amount of freshwater (this includes lakes, rivers, and streams). Another 68.7% of all freshwater is locked away in glaciers, while 30% of freshwater is located within the pores of the ground in the form of groundwater (US EPA, 2013). Approximately 64% of the world's population is expected to live in water-stressed basins by 2025 (Steinfeld et al., 2006).

Water shortage in China (photo from The Guardian)

Freshwater is extensively used in livestock agriculture, the most significant use coming from the irrigation of crops for intensive feeding operations. The livestock sector is a key player in increasing water use and represents 8% of global human water use (Steinfeld et al., 2006). For instance, approximately 16,000L of water are needed to produce 1kg of beef (Janzen, 2011). In terms of water pollution, the major sources from the livestock sector include animal waste, antibiotics and hormones, chemicals from tanneries, fertilisers and pesticides for feedcrops, and sediments from eroded pastures. These pollutants contribute to freshwater eutrophication, coastal dead zones, and the degradation of coral reefs, among others (Steinfeld et al., 2006).

As I mentioned above, these are only some of the many environmental impacts of livestock agriculture. Livestock's Long Shadow by Steinfeld et al. is currently the most comprehensive study on the environmental impacts of the livestock sector. I strongly recommend flipping through it if you're eager to learn more on the topic.

Having read about some of the environmental impacts arising from the livestock sector, what do you think are potential solutions for a more sustainable food industry? 

Thanks for reading!

Are Humans Becoming More Carnivorous?

Photo courtesy of Farming America

At the beginning of December, Nature News published an article titled Humans are becoming more carnivorous. The article discussed how global meat consumption has increased since the 1960s. The article describes the findings of a new study, Eating up the world's food web and the human trophic level published by Bonhommeau et al. (2013) in the peer-reviewed journal Proceedings of the National Academy of Sciences.

Bonhommeau et al. (2013) used the trophic level concept to quantify human diets. Trophic levels are often used to define the roles of species in ecosystems by describing the energy levels associated with primary producers, secondary producers, and tertiary producers (Kercher and Shugart, 1975). Species belonging to the lowest trophic levels are primary producers (e.g. algae, plants), and species belonging to the highest trophic levels are top predators. When moving from one trophic level to another, a loss in energy occurs (Kozlovsky, 1968). Bonhommeau et al. (2013) calculated the Human Trophic Level (HTL) for the very first time using human food supply per food item per capita per year national data from the Food and Agriculture Organisation (FAO). The data represent 98.1% of the world population between 1961 and 2009.

Their results indicate a 3% increase in HTL since 1961 (as shown in the figure below). By using a weighted average to represent different countries' populations, the researchers found that much of this increase was driven by China and India (HTL increase of 7.4%). 

A) Trends in the HTC (1961-2009) and B) Map of the median HTC level over 2005-2009 (Bonhommeau et al., 2013) 

Although there is a considerable amount of inter-country variability within the results, cluster analysis has shown that there are five different groups of HTLs:

The first group includes sub-Saharan countries and Southeast Asia and exhibits patterns of low and stable HTLs due to that fact that populations in these regions have mainly plant-based diets. The second group includes countries from Asia, Africa, South America, including China and India, and exhibits low but increasing HTLs. The third group includes Central America, Brazil, Chile, Southern Europe, several African countries, and Japan. It has higher HTLs than group 2 and exhibits an increasing trend. The fourth group includes North America, Northern and Eastern Europe, Australia, and New Zealand, and has high and stable HTLs until 1990 which increase thereafter. Finally, the fifth group possesses the highest overall HTLs and decreasing trends, and includes Iceland, Scandinavia, Mongolia, and Mauritania.

In addition to the trends described above, the results found by Bonhommeau et al. (2013) challenge the classic view of humans as top predators - based on their analysis, humans were placed on the same trophic level as anchoveta and pigs (level of 2.21). The researchers also found that the trophic level of terrestrial animals consumed by humans has only slightly increased, while the trophic level of marine food items has decreased due to declines in the mean trophic level of marine fisheries catches. 

When I first read the article in Nature News, I was a little bit surprised to learn that global meat consumption has increased despite so much recent emphasis on meat consumption reduction, for example through campaigns such as Meat Free Mondays. However, reading through the results, the numbers do add up. When looking at the bigger picture and taking into account the economies of different countries, we still see a growing preference for a western-style diet. 

What does a global increase in meat consumption imply? I'll be back to explore the potential environmental impacts in the next post.

Thanks for reading!