Two major natural catastrophes, besides COVID-19, recently occurred in India—Locust attack in the West and Amphan cyclone in the East. At the one end, unseasonal cyclones are intruding further into the land, while at the other end, invasion area of locusts is expanding. The nature of the two events appears isolated but inter-linked through climate change.
The article attempts to find these inter-linkages. Is there a probability that unseasonal cyclones like Amphan can further invite locust attacks to expand in other parts of India?
On May 20, 2020, Cyclone Amphan hit eastern India and neighboring Bangladesh. Killing at least 88 people, it affected over ten million people in the eastern Indian state only. Millions of Indians and Bangladeshis were evacuated and left powerless, water-less, and several roofless.
This speed surpasses the previously reported speed of ‘super cyclone’ that slammed into Odisha on October 29, 1999, with wind intensity of up to 260 kmph.
The year 2019 and 2020 saw back-to-back severe pre-monsoon cyclonic storms.
Prior to this, in the Bay of Bengal, Maarutha and Mora formed in April and May 2017, and before that Cyclone Roanu formed in May 2016. But none of these made landfall over the Indian coast. In fact, Mora weakened into a cyclonic storm and further into a depression, and Maarutha showed the shortest life span.
But Amphan intensified from a category I cyclone to category V in a short span of 18 hours.
In the first two weeks of May 2020, the Bay of Bengal registered more than the usual maximum sea surface temperatures of 32–34 degrees Celsius, which was prior to the formation of cyclone Amphan. The surface temperature over the sea above 28°C acted as a threshold for deep atmospheric convection.
High ocean temperature acts as cyclone fuel. Even a small rise in sea surface temperature causes more vapors, making the cyclones more intense. Hence, long term availability of high ocean temperatures led by unusual warming may have caused this cyclonic intensification.
Tropical cyclones have lately shown unusual characteristics such as an unexpected change in direction, more intensity and higher speed. Heat energy pockets in the ocean contribute to changing the direction, influencing the speed and the intensification of a cyclone.
It is suggested that as we go away from the Equator, seawater becomes cooler towards the poles. As a result, tropical cyclones do not get enough energy to move further and weaken up. But in the wake of unusual warming, the cyclone will find a line of favorable temperature to move further towards the poles. Also, Earth’s rotation supports the spinning of a cyclone, and this rotating effect keeps increasing as we go from the Equator to the poles.
Now, these two factors—unusual warming and Earth’s rotation, may contribute to increasing the storm range. The Nature study by NOAA National Climatic Data Center also points towards the poleward trends.
For instance, the historical data shows the Indian Ocean cyclones moving further south and closer to places like South Africa. The gradual warming of the Indian Ocean is the suspected reason.
These intensifications and unpredictable moving trends of cyclones are highly dangerous, increasing vulnerability of the less prepared, less-cyclone prone poor community.
Another catastrophe is the huge Locust Plague that has been wreaking havoc on two South Asian countries—India and Pakistan.
Locusts, the ravenous grasshoppers, exhibit swarming behavior and can be 460 square miles in size. Such swarms can drastically devastate crops, as a desert locust can consume about 2 grams per day, and there can be as many as 80 million locusts in a swarm.
Large swarm attacks can result in huge agricultural losses, leading to famine and starvation.
As the swarms of locusts devour every plant material in their path, how horrific is the situation for a farmer since there is no adequate mechanism available so far to deal with this mammoth situation, may it be in India or Pakistan?
The much recent locust attack of 2020 has so far destroyed 1,23,000 acres of cropland in Rajasthan and Madhya Pradesh and impacted up to 40% of the crops in Pakistan. Pakistan has declared a national emergency over the invading locust swarms, just like the African country, Somalia. The infestation had resulted in the destruction of more than 1,75,000 acres of farmland in Somalia by Dec 2019.
For low-income countries with fragile food security systems and lack of coping mechanisms, locust waves threaten to starve poor farmers.
If we closely observe the unexpected infestation patterns, we will find India and the neighboring country of Pakistan suffering its worst locusts attack since 1993. For Kenya, a country under the Horn of Africa, it is the worst invasion in 70 years.
Current locust attack has been the worst plague in recent history.
If we go back to 2018, we find how a series of unexpected cyclones brought unusual rainfall in arid regions of the Arabian Peninsula.
Cyclone-driven unseasonal rainfall helped the vegetation bloom. The locust found enough food to prosper, and moist sandy soil and exceptionally wet weather favored breeding. As a result, by the year 2019, the locust population folded 8000 times. This huge locust swarm then splits into two directions. While one locust wave moved to Southern Iran and later entered Pakistan and India, the other wave hit the Horn of Africa, entering Kenya.
The migratory pests had intruded Western Rajasthan and Gujarat in the last two decades with one major invasion last year. But this year, Rajasthan witnessed an early summer attack as the first case got reported on May 1, which is way before the expected month of June. Unlike past years, 2020 is witnessing locust menace extending into Madhya Pradesh, Uttar Pradesh and Maharashtra.
The abnormal monsoon arrival in Western Rajasthan that has brought greenery and breeding opportunities for locusts is suggested to be a reason for this locust expansion. With a capacity to fly as far as 150 km a day, they are fast migrating to other parts of India in search of food.
On May 28, 2020, large swarms of locusts stretching up to 17 kms in length and 2.5 km in width entered farms in Nagpur district of Maharashtra. This swarming behavior is a sign of hunger and a response to a desperate search for food pastures.
In “solitary” form, locusts are relatively harmless to crops, typically displaying green colour. But certain environmental conditions trigger them to show swarming behavior. As a swarm, they start showing aggressive mob traits, switching their color from green to brown/black.
These certain conditions are created by abnormal rains in desserts. As rain pattern becomes unsustained, the food availability for already multiplied locusts becomes scarce. The desperation and deprivation bring thousands of locusts to feed on one single vegetation patch. This close crowding triggers behavioral changes. For survival, they actively seek each other’s company. Locusts thus tend to form bigger groups to increase group stability and reduce vulnerability. Driven by hunger, they break their recession area.
This recession area or their core region was normally limited to the African Sahel to the west and Rajasthan to the east. But today, herds of locusts are reaching districts like Vidarbha, Maharashtra, for the first time in recent Indian history. This is a strong indicator of locusts expanding their invasion area.
Swarms move under the influence of weather conditions, particularly seasonal wind and rainfall.
Strong air circulations brought by cyclones from the surrounding areas can create bigger swarms. The wind can concentrate the scattered locust population or survivors from multiple swarms. Locust populations can get concentrated in areas of convergence to give rise to swarms of locusts that may get dispersed due to divergent wind.
Either way, wind is an important factor in swarm formation and movement.
In May-end, Madhya Pradesh and Uttar Pradesh experienced a locust attack after 27 years. These states, including Rajasthan, were receiving unseasonal rainfall in March, April till mid-May. Along with unseasonal rainfall came north westerly winds due to Cyclone Amphan.
It is speculated that rainfall favored rapid insect multiplication, while wind helped locusts reach regions they rarely impacted.
Locusts favor warmer winds associated with atmospheric depressions. In these cases, prevailing seasonal winds might not be such an influential factor. As deep depression intensifies into a cyclonic storm, it brings larger amount of water and moist wind. This further creates an ideal situation for locusts to move beyond their boundary.
With the rise in global temperature and climate change, a never-ending cycle of cyclonic disturbance and pest infestation are leading to a deadly future.