Here I bring the second article of the series on "Plant Health". This campaign is the awareness series on environmental impacts on plants and agriculture. Locust swarm has been a great threat and its swarm are recently been spotted in Nepal too. They can cause tremendous loss of vegetation and agriculture and climate change is supposed to result and escalate locust swarm.

Desert Locusts (Schistocerca gregaria) increases in number and change their behavior from solitarious individual insect to gregarious group forming a swarm when good quantity of rains falls and green vegetation develop. A swarm of locusts spread across an area of one square kilometer can eat as much food as 35,000 people in one day with each locust insect able to eat its two-gram body weight in food each day. Locust swarm has affected central and eastern Africa and Middle East and south Asia. Food and Agriculture Organization has warned that rising numbers of desert locusts present an extremely alarming threat to food security and livelihoods as locust swarms are consuming enough crops to threaten the food supply of millions of people.

The swarms first arrived in the Horn of Africa at the end of summer 2019. They had moved in from the Arabian desert, where good breeding allowed them to multiply by surprising 8,000-fold. The current situation and forecast are alarming as locust infestations are expected to extend to other areas in the Horn of Africa and southwest Asia. There have been six major Desert Locust plagues in the 1900s, one of which lasted almost 13 years with the last major plague seen in 1987-89 and last major upsurge seen in 2003-05. The FAO has estimated that the current outbreak is the largest seen in 70 years in Kenya, 25 years in Somalia and Ethiopia and 30 years in Pakistan.

Desert Locust are always present somewhere in the deserts between Mauritania and India. Desert Locust are closely associated with rainfall, winds and vegetation. Several successive seasons of breeding can occur when widespread or unusually heavy rains fall in adjacent areas with increase in populations developing into locust swarm and locusts can increase further and extend to other areas. The favorable conditions for locust breeding are: moist sandy or sand/clay soil to depths of 10-15 cm below the surface, some bare areas for egg-laying, and green vegetation for hopper development.

Temperature governs the speed of locust development as studies have linked a hotter climate to more damaging locust swarms. The temperature of earth tends to rise every year although Paris Agreement Paris targets to keep the increase in global average temperature to well below 2 °C above pre-industrial levels and to pursue efforts to limit the increase to 1.5 °C, recognizing that this would substantially reduce the risks and impacts of climate change. Climate expert predict that increased temperatures associated with climate change can shorten both the long maturation and incubation periods during the spring in Locus. Climate change experts predict more extreme weather including droughts, floods and cyclones along with the increase in global temperature which can contribute to proliferation of the destructive insects. With climate change it is possible that increasing aridity or changes in rainfall patterns could lead to locusts expanding their usual geographical range Conditions favoring outbreaks are becoming more common.

FAO director-general Qu Dongyu said, “Despite control operations, recent heavy rains have created ideal conditions for the pest’s reproduction in several countries”. The Horn of Africa was hit by eight cyclones in 2019 with 300% above average rainfall between October and mid-November. Rainfall was up to 400% higher than average in Kenya. As the locust moved through East Africa, the region was hit by unusually wet conditions and more cyclones which allowed swarm to increase. These abnormal rains were caused by the Indian Ocean dipole, a phenomenon accentuated by climate change. This suggests, locust swarm outbreak has its roots in the unseasonal heavy rains caused by climate change. According to the government of India’s Locust Warning Organization (LWO), the attack this year is highly irregular as it has come earlier than usual and reached farther. António Guterres, the UN’s secretary general also said in a statement, “There is a link between climate change and the unprecedented locust crisis plaguing Ethiopia and East Africa. Warmer seas mean more cyclones generating the perfect breeding ground for locusts. This is getting worse by the day.”

At present the primary method of controlling Desert Locust swarms and hopper bands is with mainly organophosphate chemicals. Extensive researches are still going on regarding biological control and identification of relation of locust swarm with climate change. Investigations and research need to continue to analyze current and past survey data in order to identify changes in rainfall patterns, locust development periods, and outbreak frequency.

References

Agarwal, K., & Shurti, J. (2020). Science The Wire. Retrieved from Climate Change Brings the Worst Locust Attack in Decades to India: https://science.thewire.in/environment/locust-attack-india-jaipur-climate-change/

Dunne, D. (2020). CaronBrief. Retrieved from Q&A: Are the 2019-20 locust swarms linked to climate change?: https://www.carbonbrief.org/qa-are-the-2019-20-locust-swarms-linked-to-climate-change

FAO. (2020). Locus Watch Desert Locus. Retrieved from Food and Agriculture Organization: http://www.fao.org/ag/locusts/en/info/info/index.html

Stone, M. (2020). National Geographic. Retrieved from A plague of locusts has descended on East Africa. Climate change may be to blame.: https://www.nationalgeographic.com/science/2020/02/locust-plague-climate-science-east-africa/

UNEP. (2020). Locust swarms and climate change. Retrieved from UN Environment Programme: https://www.unenvironment.org/news-and-stories/story/locust-swarms-and-climate-change

Picture: https://necjogha.com/2020/02/10/locust-swarms-and-climate-change/