Climate change is hurting farmers – even seeds are under threat
Climate change is already affecting the amount of food that farmers can produce. For example, crop sowing in the UK was
delayed in autumn 2019 and some emerging crops were damaged because of wet weather
. Meanwhile in Australia, considerable drought
has been immensely damaging
But climate change can also have a knock-on impact on farming by affecting the quality of seeds, making it harder to
establish seedlings that then grow into mature, food-producing plants. My research group has recently published a study
showing that even brief periods of high temperature or drought can reduce seed quality in rice, depending on exactly
when they occur in the seed’s development.
Nonetheless, it is possible to breed improved varieties to help crops adapt to the changing climate. And the resources
needed to do this are being collected and conserved in “genebanks”, libraries of seeds conserving crop plant diversity
for future use.
In much of the developing world in particular, the supply of affordable, good-quality seed limits farmers’ ability to
establish crops. Seeds need to be stored between harvest and later sowing and poor-quality seeds don’t survive very long
in storage. Once planted, low-quality seeds
are less likely to emerge as seedlings and more likely to fail later on, producing a lower plant density in the field
and a lower crop yield as a result.
For this reason, investigating seed quality is an important way of assessing such effects of climate on cereal crop
production. We already know that climate change can reduce the quality of cereal seeds used for food
, food ingredients
and for planting future crops
The main factor that affects seed quality in this way tends to be temperature
, but the amount and timing of rainfall is also important
. This impact can come from changes in average weather patterns, but short periods of extreme temperature or rainfall
are just as important
when they coincide with sensitive stages in crop development. For example, research in the 1990s
revealed that brief high temperature periods during and immediately before a crop flowers reduces the number of seeds
produced and therefore the resulting grain yield in many cereal crops.
Hot spells can make rice seeds less likely to become seedlings. FenlioQ/Shutterstock
has now confirmed that seed quality in rice is damaged most when brief hot spells coincide with early seed development.
It also revealed that drought during the early development of the seeds also reduces their quality at maturity. And,
unsurprisingly, the damage is even greater when both these things happen together.
In contrast, warmer temperatures later in the maturation process can benefit
rice seed quality as the seeds dry out. But flooding that submerges the seed can also cause damage, which gets worse
the later it occurs during maturation. This shows why we have to include the effects of changing rainfall as well as
temperature and the precise timing of extreme weather when looking at how seed quality is affected.
Our research has also shown that different seed varieties have different levels of resilience to these environmental
stresses. This means that farming in the future will depend on selecting and breeding the right varieties to respond to
the changing climate.
The world now has a global network of genebanks storing seeds from a wide variety of plants, which helps safeguard their
genetic diversity. For example, the International Rice Genebank
maintains more than 130,000 samples of cultivated species of rice, its wild relatives and closely-related species,
while the AfricaRice genebank
maintains 20,000 samples.
Our finding mean that, when scientists breed new crop varieties using genebank samples as “parents”, they should include
the ability to produce high-quality seed in stressful environments in the variety’s selected traits. In this way, we
should be able to produce new varieties of seeds that can withstand the increasingly extreme pressures of climate