The Environmental Impacts of Farming: The Consequences of Feeding Seven Billion

After last week’s trip to the symposium I think it is time to get back into the core of what this blog is about. Today I will revisit the environmental impacts of farming that I mentioned briefly in my first post. I hope to explore solutions to the following issues in future posts, but for now here are the facts:

Biodiversity
Agriculture is one of the biggest threats to wild plant and animal species.
Maxwell and colleagues showed that overexploitation and agriculture were the most serious threats to the 8,688 threatened or near-threatened species on the IUCN red list . Agricultural activity alone threatened 5,407 species whereas climate change was found to affect ‘just’ 1,688 in comparison. The Royal Botanical Gardens, Kew reported that livestock farming, logging and expansion/intensification of crop farming are the biggest threats facing vascular plant species, illustrated here: 

Climate change

Agriculture is responsible for 18% of all greenhouse gas production.

Making rearing cattle more damaging than driving cars. If we look at three of the most abundant greenhouse gasses individually, the livestock sector is responsible for:

•  5% of anthropogenic carbon dioxide emissions.
• 44% of anthropogenic methane emissions (with 23 times the Global Warming Potential (GWP) of CO2).
• 53% of anthropogenic nitrous oxide emissions (with 296 times the GWP of CO2).

If we break this down further, the largest emitters in agriculture are:

Genetic erosion

Over the last century, crops have lost around 75% of the their genetic diversity.

Currently just 30 crops constitute 90% of the calories we consume, and only 14 animal species make up 90% of our livestock. This is a major threat to food security as genetic diversity is essential for the survival of a species when environmental conditions change. Some argue that a food crisis is inevitable due to this lack of genetic diversity. Here is a more detailed overview that includes examples of crops impacted by genetic erosion such as finger millet.

Wheat – the most widely grown crop. GRDC.

Land use

Just under half of the world’s habitable land is used for agriculture. 

This has dangerous implications for biodiversity. Some agricultural ecosystems, especially those seen with traditional farming, provide essential habitats for wild plant and animal species. However, the rise of intensive farming has led to the destruction of important habitats and their replacement with monocultures.  For example, cattle ranching is responsible for the majority of deforestation in Latin America, and the conversion of land to palm oil plantations in Southeast Asia is threatening endangered species such as tigers and the Asian elephant. Aquaculture is having a similar effect on wild marine populations, for example intensive shrimp farming has led to the clearance of mangrove forests in Asia and Latin America. 

As well as the impact agricultural land use has on biodiversity, unsustainable practices are leading to the loss of around 12 million hectares of land per year due to desertification. Soil erosion and degradation is a serious issue, with fertile soil being lost at a rate of 24 billion tons per year. With the population only growing, and the land we can use to feed us shrinking we have a serious problem on our hands.  

Clearing for palm oil plantations in Sumatra. National Geographic.

Pollution

Agriculture is the leading contributor to pollution in many countries.

As well as agriculture’s 18% share in greenhouse gas emission it also pollutes the environment in other ways, for example through animal waste and its use of pesticides and fertilisers. Animal waste is one of the main contributors to air, soil and water pollution, with US livestock alone producing 335 million tons of ‘dry matter’ per year.

The amount of pesticide used on fields has increased by 26 times over the last 50 years. While pesticides target specific pests, they can often have a more harmful effect on the species that naturally prey on the pests as well as pollinators essential for over a third of the food we eat.

The most damaging effect of nitrogen-based fertilisers is eutrophication. This happens when fertilisers are washed off land into rivers and lakes leading to a dramatic increase in nitrate or phosphate levels, which in turn induces growth of plants and algae in the water. The overgrowth of these plants reduces oxygen levels, which can suffocate animal life. These areas are often referred to as ocean ‘dead zones’.

Algae bloom in California. National Geographic. 

Water consumption

Farming accounts for 70% of available freshwater consumption.

While water is a finite resource, much of its use is wasteful and unsustainable. Chartzoulakis and Bertaki describe how inefficient water use is in agriculture, with 35% being lost through irrigation, field application and farm distribution. Many countries are reaching (or have reached) their renewable water resource limits such as the US, China and India. Also, the demand for water is estimated to increase 19% by 2050, so it is another important area to explore.

I hope you’ve found this overview useful and have a look at the links for more detail. Of course I couldn’t cover everything so let me know if you think I have missed anything important in the comments!

Cover images from Wikimedia Commons