We tend to paint the impact of climate change using big, brash strokes: jacked-up storm systems with terrifyingly violent winds, vast fields scorched and cracked by drought, the raging momentum of floods, the heartbreaking loss of lives, and the jaw-dropping destruction to property and commerce. We have been accustomed to seeing the mega-devastations that we overlook the silent existential threats—like an ever tightening noose—that will profoundly affect us if we do not act. One significant impact of climate change that is almost unnoticed because you do not see it splattered across news headlines is how it affects plant health.
Through their ability to photosynthesize, practically all ecosystems depend on plants as the critical foundation of food chains. Of the more than 400,000 species of plants on earth, at least half of which are edible for humans—although it is possible that we are capable of eating 300,000 plant species, according to the World Economic Forum.
Providing sustenance is just one of the multitudes of benefits we get from plants. There are at least 28,187 plant species officially recognized for their medicinal uses but fewer than 16% are cited in official publications that provide detailed descriptions and tests to identify and assess the quality of plants used in herbal drugs. Aside from making up to 80% of the food we eat, plants also produce 98% of the oxygen we breathe, according to the United Nations Food and Agriculture Office (FAO).
International effort to protect plant health
However, plants are under constant and increasing threat from pests and diseases and for this reason the FAO declared 2020 as the International Year of Plant Health (IYPH), an opportunity to raise global awareness on how protecting plant health can help end hunger, reduce poverty, protect the environment, and boost economic development.
“Plants provide the core basis for life on Earth and they are the single most important pillar of human nutrition”, said FAO Director-General Qu Dongyu, “But healthy plants are not something that we can take for granted.”
On 28 January 2021, One CGIAR held a webinar, Climate change and plant health: impact and the role of research, as the first of its International Year of Plant Health webinar series. The seminar served as a platform for discussing the anticipated impacts of climate change on plant health in smallholder systems; tackling how the occurrence, intensity, and frequency of biotic and abiotic stresses will change as a function of climate change; and the role of research in providing support to global efforts to mitigate or adapt to climate change challenges for plant health.
A clear and present challenge for humanity
“Human driven climate change is the challenge of our time,” Abdelbagi Ismail a principal scientist at the International Rice Research Institute (IRRI) and its representative for Africa, said during the webinar. “It poses grave threats to the bedrock of any society agriculture extremely events such as heat, drought, and floods, can make plants more vulnerable to pests and diseases and changes in local weather patterns can generate conditions favorable for the spread of these plant pests and diseases. We know that climate change will seriously affect the small-scale farmers households throughout the developing world.”
The link between climate change and increasing incidences of pests and diseases has been documented by plant researchers. “In general, an increase in temperature and precipitation levels favors the growth and distribution of most pest species by providing a warm and humid environment and providing necessary moisture for their growth,” said Dr. Tek Sapkota, an agricultural systems and climate change scientist at the International Maize and Wheat Improvement Center (CIMMYT), in Pests and diseases and climate change: Is there a connection?
Climate change also wreaks havoc on genetic diversity within populations and species as it significantly alters the current environmental landscape and, consequently, the distribution of plants and associated species, genetic flow, biodiversity, population sizes, and life cycles.
“For plant breeders, pests and diseases could eradicate native genetic resources which are potential sources of resistance genes to combat the threats,” Dr. Ismail added during his webinar segment.
Insects and climate change
Pranav Baskar of NPR reported on the scourge of hundreds of millions of desert locusts (Schistocerca gregaria) found mainly in Africa, through Arabia and West Asia, of “Biblical scope” that attack East African countries in 2020:
Titanic swarms of desert locusts resembling dark storm clouds are descending ravenously on the Horn of Africa. They're roving through croplands and flattening farms in a devastating salvo experts are calling an unprecedented threat to food security. On the ground, subsistence planters can do nothing but watch — staring up with horror and at their fields in dismay
Is there a link between the massive invasive pests and climate change?
Experts believe that the occurrence of three tropical cyclones over eastern Africa and the Arabian Peninsula in 2018, a rare weather anomaly in the region, enabled the insects to breed in great numbers.
Typically, almost half of storm systems in the region dissipate without making landfall, or moving ashore and only about one in three storms move toward the Arabian Peninsula. But in 2018, two cyclones hit Yemen (Sagar and Luban) and Oman (Mekunu). Cyclone Mekunu, particular, brought heavy rainfall that turned parts of the arid Rub' al-Khali desert into freshwater lakes, an event that has not happened in almost two decades, and provided a favorable breeding conditions that led to the locust infestation that affected 10 countries two years later.
However, in his webinar presentation, Henri E.Z. Tonnang of the International Center of Insect Physiology and Ecology, said the relationship between insect pests and climate change is really far more complex with numerous moving parts.
“We assume that the effect of climate change on insect pests is huge but we are only starting to fill what these effects may be,” Dr. Tonnang said. “Temperature change is said to have a massive impact on insect and temperature increase may lead to increase in metabolism rate, reproduction rate, and in different change within nature. There is also very little known on the impact of very little or no precipitation. We need to look at it holistically or integrate all the different components involved in crop production to properly understand the entire impact.”
In addition, the uncertainty in climate predictions poses a major limitation in comprehending this relationship. “We use more data but those climate change models are not always perfect,” he added.
Plant diseases and climate change
In her segment on climate change and diseases, Karen Garret, preeminent professor of plant pathology at the University of Florida, said understanding where risk will change poses a big challenge.
“Management is often a challenge already without a change,” said Dr. Garret. “With climate change, we need to understand how we shift our strategies for disease management.”
For pests and pathogens, one of the most important risks is the movement into new areas. Since 1960, crop pests and diseases have been moving to the earth’s north and south at an average of 3 kilometers a temperatures increase. For example, Tar spot, a destructive fungal disease of maize caused by Phyllachora maydis normally prevalent in tropical climates of Latin America, has been detected in non-tropical regions and, by 2015, has entered the U.S. Wheat rusts, one of the most important threats to wheat production, are also adapting to warmer climates and becoming more aggressive. Other pathogens creeping into new territories include Fusarium oxysporum (Fusarium wilt) and cassava mosaic disease.
Another way diseases spread is through planting materials and food that are part of relief efforts during times of crises caused by extreme weather events.
A strategy for confronting climate change shocks and risks
However, amidst all the gloom and doom, One CGIAR launched a new strategy that puts much greater focus than ever before on confronting shocks and risks to food and farming systems.
“These could be market collapses, disease epidemics, the pandemic we're seeing now, and more and more importantly, climate risks,” said Dr. Sonja Vermeulen, the director of programs at the CGIAR system management organization. “The strategy recognizes that standalone solutions, however brilliant they might be, won't be enough to make food systems resilient. We need whole systems solutions that consider plants, animals, ecosystems and people together. And this is exactly the approach that unleashing the potential of plant health we'll take. The ultimate goal is to increase farm incomes and to create new jobs and new businesses that benefit poor people, women, and youth.”
Dr. Garret also highlighted a need to integrate global databases and global models for interpreting them to have the best strategies to evaluate where risk is changing, where diseases are becoming more important for surveillance, predict future outbreaks.
Armed with the right data, a global surveillance system for crop diseases can empower countries and regions to quickly launch coordinated responses to emerging disease outbreaks to prevent disease establishment and contain the pathogens. Ultimately, the global surveillance system can help stabilize global food supplies while boosting global food protection.
“Within CGIAR, there's a platform for big data and agriculture which can be key for this sort of global integration,” she said. “Universities like my own university can make great contributions to this as well. For example, University of Florida has a new artificial intelligence initiative. And I think a lot of institutions are investing in that as well.
“One thing that we can do to counterbalance and integrate with models have changed risk based on climate is also changed risk based on cropping patterns and how they affect cropland connectivity,” she added. “One of our interests in and collaborating with CGIAR scientists is to look at how the spatial distribution of crop lands, influences risk, and how that combines with risk due to climate.”