Mycotoxins and climate change: is agribusiness ready for the impact?
The Sixth Assessment Report of the Intergovernmental Panel on climate change is unequivocal, clearly stating that it is a result of anthropogenic activity:
Earth’s climate is undergoing adverse global changes.
These changes are characterized by changes in:
Temperature.
Precipitation.
Atmospheric CO2 concentration.
The impacts of global warming are expected to impact a diverse range of industries.
The projected impact on crops worldwide is severe, affecting not only food security, by reducing yields and therefore crops availability, but also its safety.
In this scenario, mycotoxins are considered by many experts as the most important food safety hazard as direct consequence of climate change.
Greenhouse Gases and Global Warming
Anthropogenic greenhouse gas (GHG) emissions have reached historical highs. These gases are the result of Human activities such as:
Fossil fuel combustion.
Deforestation (CO2).
Agriculture and livestock (CH4).
The use of nitrogen-based fertilizers (N2O).
The atmospheric concentrations of carbon dioxide (CO2), methane (CH4) and nitrous oxide (N2O) have signiicantly increased their concentrations in the atmosphere.
These gases are considered the main sources of pollutants behind global warming as they absorb and re-emit infrared radiation through the greenhouse effect, a process that increases the retention of heat in the Earth’s atmosphere.
ATMOSPHERE
GREENHOUSE GASES
GREENHOUSE EFECT
Sunlight reflected by the surface
Sunlight reflected back to space by the atmosphere
Greenhouse gases trap the heat from the sun
Sunlight absorbed at surface
Greenhouse gases released by human activity
Deforestation (CO2) Fossil fuel combustion Agriculture and livestock (CH4)
The use of nitrogenbased fertilizers (N2O)
Upon absorbing solar energy, the Earth’s surface emits heat in the form of longwave infrared radiation.
CO2, CH4 and N2O, molecules, due to their molecular structures, effectively absorb this radiation and re-emit it in all directions, including back toward the Earth’s surface.
This process amplifies the greenhouse effect, leading to a net increase in surface temperatures.
Furthermore, the effectiveness of these gases in driving global warming is influenced by their global warming potential (GWP) and atmospheric lifetimes.
Methane, for instance, has a GWP approximately 25 times greater than that of CO2 over a 100-year period, while N2O has a GWP roughly 300 times greater than CO2.
Despite their lower concentrations, these gases are potent contributors to the greenhouse effect.
However, CO2’s long atmospheric lifetime, spanning centuries, makes it the dominant driver of long-term warming.
What to expect?
Climate change is generally characterized by shifts in temperature, precipitation patterns, and atmospheric CO2 concentrations.
However, in our context, it is crucial to quantitatively assess the specific projections of these changes and their impact on crop production efficiency and quality, particularly in relation to mycotoxin occurrence.
Climate modelling is highly dependent on the scenarios for its projections and literature reports slightly different conclusions. However, generically is consensual the following changes:
CO2 CONCENTRATIONS
CO2 CONCENTRATIONS are expected to increase unless significant global mitigation efforts are made.
Current projections, based on varying emission scenarios, suggest that CO2 concentrations could exceed 900 parts per million (ppm) by the year 2100.
This scenario assumes no significant reduction in fossil fuel use or deforestation, leading to a continued rise in greenhouse gas emissions.
In the best-case scenario, an aggressive mitigation policy, CO2 concentrations could peak at around 450–500 ppm before stabilizing or declining by 2100.
TEMPERATURE
TEMPERATURE is projected to rise at an average rate of 0.03 °C per year.
Climate models indicate that by the end of the 21st century, temperatures could increase by 2–5 °C, particularly during extreme daily maximums that previously occurred once in 20 years.
The greatest temperature increases are expected over land, especially in northern high-latitude regions.
In Southern Europe, temperatures may rise by 4–5 °C, with prolonged droughts leading to reduced crop yields.
Western and Atlantic Europe could see increases of 2.5–3.5 °C, accompanied by drier, hotter summers.
Central Europe may experience a 3–4 °C rise, along with more rainfall and flooding, which could negatively impact crop yields, though extended growing seasons might offer some benefits.
In Northern Europe, temperature increases of 3–4.5 °C, along with a 30–40% increase in precipitation.
PRECIPITATION PATTERNS
PRECIPITATION PATTERNS are projected to change.
Increases are expected in certain regions, such as high latitudes, tropical areas, and during winter in northern mid-latitudes.
Decreases are anticipated in regions like Southern Europe, the Mediterranean, Central Europe, parts of North America, Central America, Mexico, Northeast Brazil, and Southern Africa.
Additionally, the frequency of extreme precipitation events is likely to rise, potentially leading to more intense floods or droughts in specific agricultural regions and seasons.
ATMOSPHERIC AND SOIL MOISTURE
ATMOSPHERIC AND SOIL MOISTURE will be impacted by the changes in temperature and precipitation, both through alterations in evapotranspiration.
For every 1 °C increase in temperature, atmospheric moisture content is projected to rise by approximately 7%.
Annual soil moisture levels are expected to decrease in regions such as the Mediterranean and subtropics, while increasing in areas like East Africa, Central Asia, and others experiencing greater precipitation.
These shifts in climate variables will directly affect crop development, fungal infections, and mycotoxin formation.
How can these changes impact mycotoxin occurrence in crops?
The occurrence of mycotoxins is influenced by a variety of factors, including:
Climate conditions.
Challenges associated with plants and storage.
Non-infectious factors such as the bioavailability of (micro)nutrients and insect damage.
All these elements can be both directly and indirectly affected by climate change.
Consequently, there is a consensus among researchers that climate change will inevitably influence mycotoxin levels in ways that are partially predictable, which will be the primary focus of this article. However, some factors remain inherently unpredictable.
Additionally, climate change will impact fungal species and their capacity to produce mycotoxins. Therefore, in certain scenarios, a decrease in mycotoxin risk may be theoretically anticipated as well.
Climate change effect on fungal distribution
It is very important to the remind audience that optimum conditions for growth are not always the same as for mycotoxin production.
Increased temperatures will lead to an overall increase in mycotoxigenic fungi suited to higher temperatures, such as aflatoxin-producing Aspergillus species.
For example, forecasts suggest that, within the next century, under scenarios of 2 °C and 5 °C temperature increases, Aspergillus flavus could emerge as a significant food safety concern in maize across regions such as central and southern Spain, southern Italy, Greece, northeastern and southeastern Portugal, Bulgaria, Albania, Cyprus, and Turkey.
Projections suppose that over the next 100 years, A. flavus might outcompete A.carbonarius, with aflatoxins posing a greater risk than ochratoxin A (OTA).
Changes in fungal distributions are already currently being reported and changes in mycotoxigenic fungi linked to climate change are already being observed.
Altered weather patterns were evident during the summer seasons of 2003, 2004, and 2012 in Italy, where prolonged dry and hot conditions (exceeding 35 °C) led to outbreaks of Aspergillus flavus in crops, a situation that was previously uncommon.
This species outcompeted the more prevalent Fusarium species, resulting in increased fumonisin contamination and higher levels of aflatoxin B1 (AFB1).
In France, during the exceptionally hot and dry year of 2015, A. flavus was isolated from maize samples at a notable prevalence of 69%.
Nonetheless, modern crops are frequently very resistant to infection by A. flavus and subsequent AFs contamination unless environmental conditions favour fungal growth and crop susceptibility.
Therefore, while it seems clear that increase of temperature may lead to a shift in fungal prevalence, it might not be directly correlated with an increase in mycotoxin production and other factors, such as the improvements in crops genetics, are something that has not been yet considered in prediction models.
Climate change effect on mycotoxin occurrence
Among the mycotoxins that pose significant risks to humans and animals—such as aflatoxins, trichothecenes, fumonisins, zearalenone, ochratoxin
A, and ergot alkaloids (CAST, 2003) aflatoxins are particularly notable for their high toxicity.
There is considerable research focused on how climate change may influence the levels of aflatoxins in agricultural settings.
Aflatoxins are produced in various crops by several species of Aspergillus, primarily A. flavus and A. parasiticus, can thrive under extreme climate warming conditions due to their high optimum temperature ranges.
Research indicates that the optimum temperature for aflatoxin production by A. flavus is between 24 and 30 °C, with some studies reporting a higher optimum of 32 °C on rice grains.
Additionally, there is a positive correlation between aflatoxin contamination and rainfall, as demonstrated by scientists, who found that higher precipitation in certain regions of South Texas led to more frequent aflatoxin contamination compared to areas with lower rainfall.
Moreover, increased water activity (aw) enhances aflatoxin production, with studies showing a continuous rise in aflatoxins at a w levels between 0.82 and 0.92.
Transcriptomic analyses revealed that A. flavus biosynthesis of aflatoxin B1 is more pronounced at an aw of 0.99 compared to 0.93.
As previously mentioned in relation to fungi distribution, AF’s production increase due to climate change is already currently being observed.
In Italy and Serbia, elevated levels of aflatoxins were detected in maize used for animal feed between 2003 and 2016, attributed to extreme climatic conditions, including severe droughts and high summer temperatures.
A study conducted in Romania from 2012 to 2015 highlighted significant contamination during the dry years of 2012 and 2013, particularly in the dry regions of Moldavia, the Southern Plain, and Dobrogea.
Increased rainfall has been linked to higher aflatoxin B1 levels, as evidenced by findings in Southeast, East, and Central Asia in 2017 and in India during 2006–2007.
24-32ºC
Climate change effect beyond the field
Increased climate variability is anticipated to elevate the risk of mycotoxin accumulation, affecting both crops in the field and those stored post-harvest, including in commercial and traditional storage facilities.
This heightened risk of aflatoxin and ochratoxin production in food may arise from insufficient storage and transportation conditions in shifting climate zones.
Additionally, pests in storage silos could proliferate more rapidly due to higher temperatures, generating increased metabolic water.
The presence of condensation and moist pockets can lead to mold development, potentially resulting in greater contamination with
CONCLUSIONS
Climate change has been acknowledged as a significant concern in respect to mycotoxin occurrence. However, notable knowledge gap remains, in some cases leading to broad generalizations.
Evidence indicates that climate change is likely to adversely affect crops globally, reducing suitable cultivation areas and increasing the risk of mycotoxin contamination.
In some regions, rising temperatures may render crop production unfeasible, while in areas where cultivation is still possible, plants will face suboptimal climatic conditions that heighten their vulnerability to fungal contamination.
Additionally, warmer climates are expected to favor thermotolerant species, resulting in a greater prevalence of Aspergillus species compared to Penicillium
Nonetheless, phenological changes in crop production also needs to be consider and, consequently, its interface with the mycotoxigenic fungal pathogens under climate change scenarios will further influence the levels of contamination with a specific mycotoxin.
While research output on the topic has increased significantly in recent years, several critical questions remain to be addressed:
Under which climate change scenarios will mycotoxin production patterns shift?
Will mycotoxins currently considered secondary in importance become more prevalent and significant in the future?
What will happen to masked mycotoxins?
Will current control and mitigation strategies continue to be effective in combating these evolving threats?
Should countries revise their safety recommendations regarding mycotoxin exposure, particularly those focused on currently predominant mycotoxins?
What new/emerging mycotoxins should be considered?
It is clear that we are already experiencing the effects of climate change, as changes in mycotoxin occurrence patterns are being detected.
This raises a significant question:
Are industry stakeholders and governments sufficiently aware of these shifts, and do they possess the knowledge and tools required to identify and address these new challenges?
As we move into a future characterized by unpredictability, it is more essential than ever to reinforce and adapt Good Agricultural Practices (GAP) and Hazard Analysis Critical Control Point (HACCP) management systems.
These practices must be adapted to align with new realities in order to minimize mycotoxin contamination, especially as marked environmental shifts and fluctuations become the norm.
The threats posed by these issues are particularly important for existing global players in the agrifood market, including countries such as Brazil and Argentina, as well as parts of Asia, including China and India.
These regions and certain areas in Africa are considered hotspots for the impacts of climate change. Therefore, from a food security perspective, addressing these questions is crucial for making more accurate predictions about the impacts of climate change on mycotoxin production and, ultimately, on food safety and security.
