strawberries grwon in a hydroponic system

Feeding people by farming in air

Almost all food for humans and their pets is grown in soil. It has been like this for millennia, but that might be about to change

Soil is the primary medium that gave humanity its leg up into the modern world of vast food production and billions of people. Soil took the windfall of cheap fossil fuel energy to support biomass as crops and livestock. Secure food production is why land is so valuable and the control of land is central to the integrity of society and those who rule.

Soil supports food production that delivers our calories and nutrients. Fish provide about 3.3 billion people with almost 20% of their average per capita intake of animal protein and 7% of global protein consumption. The land is where we grow most of our food.

All around the world, agricultural soils are under strain. Here are some numbers gathered for a report to the Global Environment Facility on sustainable land management.

Estimates of the extent and impact of global land degradation. Acronyms: FAO, UN Food and Agriculture Organisation; ITPS, Intergovernmental Technical Panel on Soils; UNCCD United Nations Convention to Combat Desertification. Source: Henry, B., Murphy, B., & Cowie, A. (2018). Sustainable land management for environmental benefits and food security. A Synthesis Report for the GEF (Global Environmental Facility). GEF, Washington, DC, USA.

These numbers refer to land degradation, but they mean that 40% of global agricultural soil is losing the capability to grow food. 

The UNCCD refer to land degradation as the reduction or loss of biological or economic productivity and complexity of the land resulting from natural processes, land uses or other human activities. And more formally, 

“The reduction or loss, in arid, semi-arid and dry sub-humid areas, of the biological or economic productivity and complexity of rainfed cropland, irrigated cropland, or rangeland, pasture, forest and woodlands resulting from land uses or from a process or combination of processes, including processes arising from human activities and habitation patterns, such as: (1) soil erosion caused by wind and/or water; (2) deterioration of the physical, chemical and biological or economic properties of soil; and (3) long-term loss of natural vegetation”

United Nations Convention to Combat Desertification (UNCCD)

Land is a more accessible term than soil. The land is mapped and legally owned and traded. It can be fenced and managed. A person can go and stand on a plot of land and look at it.  But the reality is that degradation refers to the properties and consequences for vegetation of soil.

These land degradation numbers mean that a significant and growing proportion of global soil used to grow food produces less biomass than it could under given conditions. 

An anthropomorphism would be to think of land degradation as unhealthy soil, not as fit or as strong as it could be. 


Growing pressure on unhealthy soil

Loss of soil health is most serious for the poor. It is acute in places where the pressure on land is increasing rapidly, particularly in Africa and South Asia.

At the current population growth rates, a country like Niger in west Africa, with 26 million people in 2022, is expected to have 65 million by 2050, more than double in a generation, and, all things being equal, reach 100 million by 2068.

line graph of human population growth in Niger to 2100

Population growth in Niger as an example of what is expected to happen in Africa over the next 50 years; lots more people. Source: World Population Review

Soil cannot grow food at the rates such increase demands. Resource limits will likely impact the shape of these population curves, and all things will be far from equal. 

But until that restriction happens, alternatives to soil are critical to maintaining food supply and helping achieve food security, especially for the poor.

Arable land in Niger is around 17 million ha, and there is only a small area left with soil suitable for arable expansion. So without any food imports or crop production, the current cropping area would need to support 1.5 persons per hectare in 2022 and 3.8 persons per hectare by 2050; 5.8 by 2068. This is below the global average of 6 people fed ha−1 but Niger is semi-arid and, even without soil degradation, cannot match the production average. For example, maize yield in Niger is around 1 t ha-1, close to the global average, but half the yield of US farms.

Land use map for southern Niger

Pattern of land use in Niger. Source: USGA Land use and land cover trends in Niger Yellow represents arable land, green is Sahelian short-grass savanna and orange is steppe

At 4% population growth, dry climate and limited scope for expansion of arable land, traditional agricultural methods, a country like Niger is unlikely to to be self-sufficient in food from soil alone. Even with careful land-use decisions, best practice land management, readily accessible fossil fuel inputs, the production systems in a dry country on the edge of the Sahara are too fragile—yield gaps are already significant, water is limiting, and soils degraded. 

Meeting the demand for calories would require imports unless alternative production methods can be found.

So what could be done?


Farming in water

Technology is helping grow food without soil.

Water-based systems to grow plants (hydroponics) that deliver nutrients to plant roots via solutions have been around for some time. Plants grown in water is great for leafy greens, tomatoes, some vegetables and strawberries. 

Combined with fish (aquaponics) neat partially closed-loop systems are possible where the fish provide nutrients to the plants and a tasty grilled tilapia to go with the salad

Currently  a niche production system, aquaponics and the various hydroponic options have the potential to scale and support food security. 

cultivating strawberries in a hydroponic greenhouse

Aquaponic systems for strawberry production decrease the need of external nutrient supply but also reduce the overall water discharge and increase water use efficiency. Photo by Anna Tarazevich on Pexels 


Farming in air

New innovations have dispensed with solutions altogether to grow plants without soil or water. Plant roots dangle in the air and moistened periodically by specially-designed misting devices (aeroponics).

This makes it possible for growers to raise crops in open-air, misty environments or mineral nutrient solutions under indoor controlled conditions instead of soil.

There are several advantages to this type of food production:

  • controlled indoor environment
  • multiple crops per season
  • increases the area available for production by growing plants in layers
  • immune to changes in environmental conditions 
  • options for recycling agricultural wastes 
  • minimal loss of agrochemicals to the environment
  • lower water use
  • lower fossil fuel use 
  • shorter supply chains

What sustainably FED suggests

Farming in the water or the sky is an option to augment food production from soil.  

We know it’s a bit out of the box. There are huge challenges to implementation and especially to scale aquaponics or aeroponics to feed whole communities of people. A hard problem but not impossible.

A key advantage is the growing population looking to find reliable food sources and ways to engage in food production. Hungry people will try anything and given a chance will apply their intellect and enthusiasm to new opportunities.

The question to ask about these technology fixes and novel solutions is this. 

Where are the nutrients, energy and materials to build and run novel infrastructure?

Even the smartest innovations are a net transfer of nutrients and energy from nature into food for people. The energy and nutrients have to come from somewhere and there has to be enough water to lubricate the process.


Science sources for this post

Shah, F., & Wu, W. (2019). Soil and crop management strategies to ensure higher crop productivity within sustainable environments. Sustainability, 11(5), 1485.

Cassidy, E. S., West, P. C., Gerber, J. S., & Foley, J. A. (2013). Redefining agricultural yields: from tonnes to people nourished per hectare. Environmental Research Letters, 8(3), 034015.


Hero image from photo by Henry & Co. on Unsplash

Mark

Mark is an ecology nerd who was cursed with an entrepreneurial gene and a big picture view making him a rare beast, uncomfortable in the ivory towers and the disconnected silos of the public service. Despite this he has made it through a 40+ year career as a scientist and for some unknown reason still likes to read scientific papers.

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