A new study is challenging one of the coffee industry’s most repeated assumptions: that robusta coffee can provide a relatively reliable alternative to arabica as climate change makes traditional coffee-growing conditions more difficult. The research argues that robusta’s ability to tolerate higher temperatures has been repeatedly confused with broader climate resilience, particularly its ability to withstand prolonged water shortages.

The distinction is important because robusta has increasingly been presented as a practical answer to the climate pressures facing global coffee production. Robusta is generally more heat-tolerant than arabica and accounts for a substantial share of global coffee supplies, with Vietnam and Brazil among its largest producers. As temperatures rise and weather patterns become less predictable, that characteristic has encouraged expectations that producers could increase robusta cultivation and reduce their exposure to climate-related losses.

The new research disputes that logic. Its lead author, Aaron Davis of the Royal Botanic Gardens, Kew, argues that previous assessments of robusta’s climate suitability contained important weaknesses, including the treatment of irrigated farmland as an indication of naturally suitable growing conditions. The study does not suggest that robusta has no advantages over arabica. Instead, it questions whether those advantages are sufficient to make the crop broadly resilient to climate change.

That distinction could become increasingly important for farmers, traders and coffee companies as water availability becomes a more serious constraint on agricultural production.

Heat tolerance does not eliminate drought risk

The central problem with the robusta climate-resilience argument is that higher temperature tolerance addresses only one part of the climate challenge. A coffee plant may withstand greater heat while remaining highly dependent on sufficient water during critical stages of growth. The new study argues that this distinction was not adequately reflected in some earlier assessments of robusta’s suitability under future climate conditions.

Research from Vietnam provides evidence of that vulnerability. A long-term study involving hundreds of robusta farmers found that drought reduced yields and significantly affected farm profitability. Farmers commonly relied on irrigation and other measures to reduce the effects of dry conditions, demonstrating that robusta production can remain viable during drought but not necessarily without substantial adaptation.

More recent research has also examined how robusta plants use water under different irrigation systems in Vietnam’s Central Highlands. The findings underline the importance of irrigation to production and raise concerns about how coffee farming will respond if dry seasons become longer or water resources become more limited.

This changes the interpretation of robusta’s supposed climate advantage. If production remains commercially viable only because farmers can provide additional water, the crop’s resilience depends partly on the availability and affordability of that water. In regions where irrigation is already under pressure, increasing temperatures could therefore create a more difficult production environment even if the plants themselves tolerate heat better than arabica.

The issue is not that robusta cannot survive warmer conditions. It is that climate resilience cannot be measured through temperature tolerance alone.

Irrigation can conceal the real climate risk

The study’s criticism of earlier research focuses heavily on the way agricultural suitability has been assessed. Irrigated farms can produce good yields even where natural rainfall patterns are not sufficient for the crop. If those farms are then treated as evidence that the region is naturally suitable for robusta, assessments of future climate resilience can become overly optimistic.

This matters particularly in major producing countries such as Vietnam, Brazil and India. These countries already have large robusta industries, but the study argues that some production areas are not naturally suitable without irrigation. The distinction becomes more significant when climate change places additional pressure on water supplies.

Irrigation is not inherently unsustainable, and farmers have used it successfully to protect production during dry periods. The problem is that irrigation requires reliable access to water, infrastructure and energy. If groundwater levels decline, reservoirs become less reliable or competition for water increases, farmers may face rising costs or restrictions on how much water they can use.

There is also a difference between using irrigation occasionally and making commercial production dependent on it. A farming system that needs substantial irrigation every year may be more exposed to water shortages than a crop grown in an area where rainfall naturally meets most of its requirements.

This is why the new study’s argument is broader than a comparison between two coffee varieties. It challenges the idea that changing the variety alone can solve the industry’s climate problem.

Rising robusta demand makes the finding more important

The timing of the research is significant because robusta has become increasingly important in global coffee markets. The variety is widely used in instant coffee and blends and has gained greater commercial attention as coffee buyers seek alternative sources of supply.

That demand creates an incentive to expand production. But if new plantations are established on the assumption that robusta can withstand climate change better than other varieties, farmers could be making long-term investments based on an incomplete assessment of future growing conditions.

Coffee plantations are particularly difficult to adjust quickly because new trees require years before they reach commercially significant production. A decision about where to plant robusta today therefore involves assumptions about rainfall, temperature and water availability many years into the future.

If those assumptions prove wrong, farmers cannot simply change crops from one season to the next. Land, irrigation systems, processing facilities and other investments may already have been committed. The financial consequences can therefore extend well beyond a single poor harvest.

The issue also affects coffee companies and traders. If robusta production proves more vulnerable to drought than previously assumed, the global supply chain may remain exposed to climate-related disruptions even as the industry increases its reliance on the variety.

That could make supply diversification more important. Instead of replacing arabica with robusta on a large scale, producers may need to use several strategies depending on local conditions, including improved plant varieties, shade management, soil conservation, irrigation efficiency and changes in growing locations.

Coffee adaptation will require more than switching varieties

The study’s wider implication is that the coffee industry may need to rethink the way it approaches climate adaptation. Moving from arabica to robusta can be useful in some locations because the two varieties have different temperature requirements and production characteristics. But it cannot be treated as a universal solution.

Research published this year has already been examining ways to improve robusta’s performance under water stress. One study in India found that grafting robusta onto selected arabica rootstocks could improve physiological performance under water-limited conditions. Such research points toward a more targeted approach in which plant breeding and cultivation techniques are used together to address specific climate risks.

Farm management will also become increasingly important. Maintaining soil moisture, improving water-use efficiency, protecting shade cover and choosing suitable planting locations can reduce exposure to drought. These measures, however, require investment and knowledge, and their effectiveness will vary according to local conditions.

For producers, the central question is therefore not whether robusta is more climate-resistant than arabica in general. It is whether a particular robusta-growing region will continue to have sufficient heat, rainfall and water availability under future conditions.

That is a much more difficult question to answer, but it is also a more useful one.

The new research does not establish that robusta will become unsuitable for coffee production. Nor does it eliminate the crop’s genuine advantage in tolerating higher temperatures compared with arabica. What it does is challenge the much broader claim that robusta can serve as the coffee industry’s dependable climate refuge.

The distinction between heat tolerance and drought tolerance is likely to become increasingly important as coffee-producing regions face more variable rainfall and longer dry periods. The evidence from Vietnam and recent research into water stress already indicates that irrigation plays a significant role in maintaining robusta production in some major growing areas.

That leaves the industry with a more complicated adaptation problem. Expanding robusta may still be commercially sensible in suitable regions, but the decision cannot be based on temperature tolerance alone. Water availability, soil conditions, local rainfall, irrigation requirements and future climate projections will all have to be considered.

The new study therefore challenges a convenient solution rather than offering a simple replacement. If climate change is altering the conditions under which both major coffee varieties can be grown, the industry’s response will have to involve better crop research, more efficient water management and greater diversification of production rather than relying on robusta as a single answer.

(Adapted from Investing.com)