What Climate Change Means for Food Lost in Transit

Around 30% of global food production is either lost or wasted, accounting for 6% of total greenhouse gas emissions (FAO, 2023; UN 2024). We tend to think of food loss as a storage problem in low-income countries, and food waste scraped off plates in wealthy ones. Less talked about are losses along efficient supply chains, in particular losses caused by weather and traffic.

Our study published in the American Journal of Agricultural Economics is the first research to causally identify the effect of weather and climate change on postharvest losses. It uses detailed data on 1.4 million truckloads of processing tomatoes—those destined for tomato sauce, paste and canned products—transported in uncovered trucks in California between 2011 and 2020.

We ask, does heat during the truck ride damage food quality?

The short answer is yes, but the full story is more nuanced and perhaps more reassuring than you might expect.

Heat hurts

Processing tomatoes are harvested mechanically and loaded into open, uncovered trailers. Trucks then travel an average of 87km from field to processing facility, taking around 80 minutes. That's not a long journey, but on a hot day, it's long enough to do some damage.

We measured quality using "limited use percent", the percent of tomatoes in each truckload that are soft, split, or squashed. At 10°C, around 0.95% of tomatoes in a load were damaged. At 40°C, that damage doubles to 1.9%. So yes, heat during transit harms product quality.

Traffic’s effect depends on temperature

We also consider the role of traffic using data from sensors buried beneath California’s major highways measuring the speed and flow of traffic. You might assume that being stuck in slow traffic is always bad, because it leaves tomatoes sitting in the sun for longer. And at high temperatures, that's exactly what happens: heavy traffic combined with heat is the worst combination for quality.

But at cooler temperatures, slow traffic is actually better for the tomatoes. Why? Because fast-moving trucks generate vibration that physically damages fresh produce. When it's cool, the extended exposure to mild temperatures is less harmful than the bumping and jolting from travelling at speed. We find that losses are minimised with a combination of cool temperatures and slow average speeds that reduce vibrational damage.

What are the economic consequences? Comparing the best possible conditions (cool temperatures, slow traffic) against the worst (hot temperatures, slow traffic), truckload revenue fell by just 0.2%. Applied to farm profits — after accounting for the fact that most revenue simply covers costs — this translates to roughly a 1.3% decline in profit per truckload under worst-case conditions.

What will warming trends under climate change mean for postharvest losses?

We use climate projections to estimate how warming temperatures might affect postharvest losses by the end of the century: when average temperature during a truckload's journey will rise to around 30°C and the share of truckloads exposed to temperatures above 35°C will double. Despite these trends, the projected increase in postharvest losses is negligible.

Harvesting and transporting tomatoes at night, when temperatures are cooler, would reduce losses. Refrigerated trucks would help too. But the margins on processing tomatoes are thin, and farmers and processors so far have revealed a preference not to use these available adaptation options. Given the negligible increase in postharvest losses we predict, these incentives won’t change much.

Why this research matters

Most research on climate change and agriculture focuses on production, particularly how heat affects crop yields (Ortiz-Bobea, 2021). Postharvest losses are an important yet understudied corner of this large literature, and we provide new insights into how weather and climate change affect agricultural supply chains. The finding that losses exist but are economically modest is, in some ways, good news. But it also underscores an important point: food loss doesn't only happen in the field. Understanding the entire supply chain is important for building food systems that are resilient to a warming world.

Access the journal paper

---

Contact Us

Sarah Whitnall: sarah.whitnall@uwa.edu.au

Recommended Resources

Whitnall, Sarah C. and Timothy K.M. Beatty. 2025. “Postharvest losses from temperature during transit: Evidence from a million truckloads.” American Journal of Agricultural Economics. https://doi.org/10.1111/ajae.70019 

References

Ortiz-Bobea, Ariel. 2021. “The Empirical Analysis of Climate Change Impacts and Adaptation in Agriculture.” In Christopher B. Barrett, and David R. Just (eds.), Handbook of Agricultural Economics, Volume 5, 3981–4073.

Food and Agriculture Organization (FAO). 2023. SDG Indicators Data Portal. https://www.fao.org/sustainable-development-goals-data-portal/data/

United Nations (UN) Environment Programme. 2024. Food Waste Index Report. https://www.unep.org/resources/publication/food-waste-index-report-2024