The threat of aridity or the lack of water resources on land affects 40 per cent of Earth’s arable lands — or about 5.7 million square kilometres — and another seven per cent, if the effects of soil erosion were added to the total, according to a new research.
The research report was published on December 9 and was released by the United Nations (UN) at the Conference of Parties (COP16) as part of the UN Convention to Combat Desertification (UNCCD) in the Saudi capital of Riyadh.
By 2040, it is projected that due to climate-change, there could be an expansion in the global arid area by 3.9 per cent and this would translate as losses of an estimated 20 million tonnes of maize, 19 million tonnes of rice, eight million tonnes of soybeans and 21 million tonnes of wheat.
Through these statistics, the report, titled The Global Threat of Drying Lands, highlighted that aridity, not drought, was considered the world’s largest single driver of the degradation of agricultural systems.
Aridity differs from drought in its nature and duration.
While droughts are short-term anomalies characterised by periods of low rainfall, often linked to high temperatures, low precipitation and reduced air humidity, aridity reflects a persistent, long-term lack of available moisture needed to sustain most terrestrial life.
“While droughts often attract attention because their dramatic and sudden declines in water availability cause direct losses in food production and spikes in food prices, aridification is subtler, and its direct effects on crop yields are harder to quantify,” the report stated.
At a global scale, a country’s proportion of hyper-arid, semi-arid and arid land was negatively correlated with its output of major crops, highlighting the fact that, even in regions where precipitation has increased, a higher atmospheric evaporative demand may negatively affect crop yields.
As per the landmark report, 77.6 per cent of the Earth’s land became permanently drier in the three decades leading up to 2020, compared to the previous 30-year period (1961-1990).
This widespread increase in drylands would eventually lead to countries dependent on food imports to ensure food security, further aggravating socioeconomic impacts.
“These countries face additional food security risks when increases in food prices make imports prohibitive or when food production crises, such as those during severe droughts, make these imports unavailable,” it added.
Scientists warned that the problems faced by agricultural systems due to aridity were expected to worsen into the future — especially in sub-Saharan Africa, North Africa and the Middle East and South Asia.
In sub-Saharan Africa, for example, between 17 and 22 per cent of current crop production could be lost by mid-century due to the impacts of increasing aridity and temperatures in a moderate emissions scenario.
Rainfed agriculture in the region will be specifically affected.
Yields of millet have been projected to decline by a quarter within the same time frame, if greenhouse gas emissions continued to be high, and in Kenya, maize production was projected to fall by as much as half by 2050, due to increased atmospheric evaporative demand across the country.