What are ecological droughts?

Subject: Geography

Section: Climatology

Drought impact in India:

India has reported a drought at least once every three years in the last five decades. It has lost between two and five per cent of its GDP due to the impacts of drought, according to a 2022 report from the United Nations Convention on Combating Desertification (UNCCD), which also included a global drought index that compared India’s drought vulnerability to that of sub-Saharan Africa.

How are droughts defined in India?

India identifies three types of droughts: meteorological, hydrological, and agricultural.

Meteorological Drought: This occurs when there is a significant shortfall in precipitation compared to the long-term average for a specific period. The India Meteorological Department defines a meteorological drought when seasonal rainfall is less than 75% of its long-term average. It’s classified as moderate if the deficit is between 26-50% and severe if it exceeds 50%.
Hydrological Drought: Defined by low water levels in surface and sub-surface sources like streams, reservoirs, and These droughts can occur even with average or above-average precipitation if water usage depletes reserves.
Agricultural Drought: This happens when a meteorological drought lasts for at least four weeks, leading to reduced soil moisture and vegetation. Signs include distress in agricultural communities, such as cattle sales, fodder shortages, migration, limited drinking water, increased demand for labor, and rising commodity prices.

For a state in India to officially declare a drought, it must meet certain criteria outlined in the Drought Manual of 2016. These criteria include rainfall deficit, dry spell duration, soil moisture, sown area, vegetation health (via remote sensing), reservoir and groundwater levels, stream flow, and socio-economic impacts.

Ecological drought:

Ecological drought is distinct from other drought types in its focus on the interconnectedness between humans and ecosystems within the context of drought.
Defined as an episodic water deficit that pushes ecosystems beyond vulnerability thresholds, ecological drought affects ecosystem services and triggers feedback in both natural and human systems.
This concept emphasizes the ripple effect caused by changes in an ecosystem due to drought, impacting communities dependent on those ecosystems for essential goods and services.
Studies in the Western Ghats have shown that persistent water deficits can distress certain tree species and alter their geographic distribution, affecting species persistence, diversity, and ecosystem function.
Drought is also increasingly linked to wildfires in the region.
The 2016 Drought Manual in India acknowledges drought’s environmental effects, like loss of forest cover, increased wildlife migration and human-animal conflicts. However, it doesn’t include specific indicators for monitoring or assessing ecological drought.