Subsistence farming is really tough – and it’s about to get even tougher

By Philip Thornton & Jerry Nelson

  • Farm work is already taking 20-30% longer due to heat stress on labourers and the time required will increase due to climate change
  • The effect of climate change on farm labour is likely to affect smallholder subsistence farmers in the global tropics the most
  • Among the adaptation options, farm mechanisation can help, but it comes with some risks and small-scale farmers will need to be supported through the transition

Before mechanisation, agriculture was a back-breaking affair and for many farmers, it still is. Much of this work is carried out in the fields or rangelands, often in full sun. Land clearing and preparation, planting, weeding and harvesting are still carried out by hand in many places. The hours of human labour needed to produce crop and livestock products each year can be prodigious, varying from a few hundred to many thousands, depending on the production system.

The ability to do productive work depends on many factors, including the worker’s health and age and the weather conditions. Combinations of high temperatures, high relative humidity, little wind and high insolation (solar radiation) can lead to heat stress, seriously affecting a person’s ability to work effectively outdoors. The short-term health impacts include dehydration, cognitive decline and in extreme cases, death; longer-term exposure can result in changes in the immune system, chronic heart disease and kidney diseases later in life and growing health care costs.

Translating heat stress in humans into potential loss of capacity to carry out physical labour can be measured by physical work capacity (PWC), often expressed as a ratio. Some places around the world have already seen significant losses in PWC over the last three decades. Parts of the Amazon region in Brazil, West Africa and East Central Africa, much of South and Southeast Asia, and parts of eastern China are already experiencing losses of 0.2 to 0.3 of PWC during the growing season. To put it another way, a task that under no-stress conditions takes a person a workday of 8 hours to perform may now take 10-11 hours.

By the end of the century, under a high greenhouse gas emission scenario, the PWC in these regions are projected to decline by as much as an additional 0.3. Regions with minimal present-day heat stress impacts could experience significant losses, including the southeast United States, much of southern South America, more areas in Africa, and more northerly areas in China.

Loss of labour capacity has critical implications for the livelihoods of farming households. And this at a time when the farming population almost everywhere is ageing, and youth are leaving rural areas seeking job opportunities in cities.

How can farmers adapt to greatly increased heat stress risk in the future? Adaptation options include shifting work to cooler times of the day, wearing lighter weight and more breathable clothing, more provision of shade and access to water both for drinking and wetting the body, and changing crop types to those that can grow in the cooler periods of the year. Some farmers may need to hire in extra labour to compensate for lost work capacity.

But a point may come when the limits are reached and food availability is reduced, even if food plants and animals can tolerate these extremes. What are the options then?  One is to greatly expand mechanization, such as using tractors for tillage, planting and weeding, thereby replacing the need for large amounts of human labour for these and other labour-intense activities. Future mechanization will have to be based on renewable electrical energy, if GHG emissions are to be reduced. Although essential, it comes with considerable risks and transition costs for small-scale farmers. One way to facilitate this transition is through farmer sharing clubs that spread the capital and maintenance costs of tractor ownership (e.g.,  Uptake of mechanization by small-scale producers could be facilitated via smaller-scale equipment such as cultivators and planters. As battery and other storage technology improves, this option will become increasingly viable. Bundled options involving agrivoltaics (using the same piece of land for agriculture and energy production) also offer intriguing possibilities for reducing heat stress risk in crops and boosting farmers’ incomes from energy production.

Another option is to utilize drones and robotics. This is not as far fetched as it may sound – drones are already being used in parts of Africa and Asia to deliver human and livestock vaccines to remote rural locations. The use of robotics in high-input production systems is increasing significantly for activities such as planting, harvesting, spraying, packing produce, and monitoring livestock movements on grassland, for example. Monitoring will increasingly be possible using small satellites; the Starlink system already offers relatively cheap internet connectivity, for example. The same solar panels that charge the batteries to operate the electric tractors can charge the batteries that power the drones, robots and monitoring systems. It may be several years before these kinds of applications are viable for small-scale producers in LMICs, but their time will come.

What needs to be done?

  • Encourage more applied research on heat stress in humans (and plants and livestock) as a key future risk, along with the economic analyses that can assist national policymakers in prioritising the adaptations that will be needed.
  • Develop participatory heat education and awareness tools and information campaigns so that agricultural workers everywhere know about the increasing risks.
  • Collectively reduce GHG emissions as quickly as we can, so that the potential risks of heat stress for humans (and livestock) is minimised.


Philip Thornton is Clim-Eat’s Research and Innovation Strategist. Jerry Nelson is Professor Emeritus, University of Illinois, Urbana-Champaign.

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