Explainer: What Are Ecological Droughts?

India has reported a drought at least once every three years in the last five decades. It has lost between two and five percent 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.

India recognises droughts arising from deficits in rainfall, groundwater and soil moisture, and resulting impacts on agricultural activities and produce, and socio-economic behaviours. Emerging research from around the world is now calling for the recognition of ecological drought, with an emphasis on the impacts not only on water, crops, and humans, but on ecosystems too. Accounting for ecological drought can help identify systemic vulnerabilities that can help improve adaptation efforts, researchers argue, especially as climate change is likely to worsen drought in India.

How Are Droughts Defined In India?

India monitors three types of droughts – meteorological, hydrological and agricultural.

A meteorological drought is when there is a shortfall in precipitation compared to the longterm average for a duration of time. The India Meteorological Department specifies that a meteorological drought is a situation when the seasonal rainfall received over the area is less than 75% of its long-term average value. It is further classified as “moderate drought” if the rainfall deficit is between 26-50% and “severe drought” when the deficit exceeds 50% of the normal value.

Rainfall is considered the biggest trigger of drought, but it isn’t the only factor that counts when it comes to declaring a drought. Hydrological droughts are defined by low surface and sub-surface water supplies, such as in streams, reservoirs and groundwater sources. They are a crucial indicator of drought conditions and can “arise even in times of average (or above average) precipitation when increased usage of water diminishes the reserves,” says the Ministry of Jal Shakti, India’s water authority.

Agricultural drought is when a meteorological drought persists for four weeks, leading to reductions in soil moisture and vegetation. Signs of distress, such as the sale of cattle, unavailability of fodder, out migration, limited drinking water supply, higher demand for labour employment and price of commodities are indications that the effects of drought have spilled over and affected livelihoods.

For states to declare a drought, they must qualify for some of the criteria laid down by the Drought Manual of 2016, which include indices on rainfall deficit, period of dry spell, soil moisture, area under sowing, vegetation detected through remote sensing, reservoir and groundwater levels, stream flow, as well as the socio-economic factors listed above.

How Is An Ecological Drought Different?

One of the seminal papers exploring the concept of ecological drought defines it as “an episodic deficit in water availability that drives ecosystems beyond thresholds of vulnerability, impacts ecosystem services and triggers feedbacks in natural and/or human systems.”

“What sets ecological drought apart is its emphasis on the interconnectedness between humans and ecosystems within the context of drought,” Deborah Bathke, a climatologist with the U.S. National Drought Mitigation Centre and co-author of the paper, told Mongabay-India over email. “Ecological drought encompasses and recognises that when drought drives changes within an ecosystem, it can create a ripple effect through the communities that depend on those ecosystems for essential goods and services.”

In India, the literature looking at the systemic effects of drought on ecosystems is limited and disparate. A 2021 study from the Western Ghats which looked at the effect of seasonal drought on the distribution of tree species found that persistent water deficits could distress wet associating species and alter their geographic distribution “with implications for species persistence, spatial organization of diversity and ecosystem function.” Another study from the Western Ghats found that drought may exert an “increasingly significant effect” on wildfires in the region.

The 2016 Drought Manual acknowledges the effects of drought on the environment, including loss of forest cover, migration of wildlife and “sharpening man-animal conflicts”, but doesn’t include any such indicators in its guideline for monitoring or assessing drought.

Diptimayee Nayak, an associate professor at the Indian Institute of Technology Roorkee, is exploring the ecological drought in the Indian context. In her paper, Is India Ready to Account for Ecological Droughts? she finds that most policies aimed at drought mitigation are not equipped to identify the signs of or address ecological drought. “Even hydrological drought, which focuses on surface and subsurface water levels, is not able to capture the corresponding effect on a peripheral ecosystem. This is the starting point,” she said.

One way of bridging the gap, according to her, is a cost-based approach of valuing ecosystem services which are beneficial to humans and the environment. “This is not necessarily about the cost of loss happening in a particular ecosystem, but also about the cost of recovery and revival, as well as the changing costs of adaptation,” she said.

Can Addressing Ecological Drought Help Climate Adaptation?

Since there is no universally accepted definition of ecological drought, metrics to monitor and assess it are still evolving. “Numerous knowledge gaps exist and the tools and data needed to monitor, forecast, and assess ecological droughts are limited,” said Bathke, adding, “Ecological systems are complex, and limited comprehensive and long-term data makes it difficult to understand how ecosystems will respond to different levels of drought severity and duration.”

For ecological droughts to remain distinct from the other categories, it needs to focus on impacts, according to Vimal Mishra, professor, civil engineering and earth sciences, IIT Gandhinagar. “Ecological drought can be thought of as the impact of all the other types of droughts on the ecology. The challenge is understanding what those impacts are, because ecosystems change from one place to another,” he said.

India already faces a number of challenges in implementing its drought policies. A study co-authored by Mishra found that drought occurrence was more frequent than drought declaration, meaning states and regions were experiencing droughts without receiving or using aid to mitigate the problem. One of the reasons for this gap is because irrigation and groundwater extraction helped maintain crop yields in some states, like Punjab, despite the environmental damage and hydrological drought it caused. Other gaps include uncertainties in the data used for the qualifying indices in the Drought Manual. “Though they are well known, a holistic view of drought and the cascading impacts of drought are not very well thought out or assimilated in the drought framework in India, from an operational perspective,” Mishra said.

According to Bathke, viewing or defining a drought without including the biome or ecosystem may cause policymakers to “enact policies or response strategies with an “either/or” mindset and pit the water uses of humans against the needs of ecosystems.”

Global warming has made drought a more common experience in India. From 1951 to 2016, drought area in the country has increased by 1.3% every year. The approach of “recognising nature as an important stakeholder,” in drought, as Nayak puts it, can help improve the resilience of ecosystems in the long run, avoid employing maladaptive practices like widespread groundwater extraction, and offer solutions to mitigate the effects of drought, she added. One of the key purposes of the Amrit Dharohar scheme, launched last year to protect wetlands across the country, for example, is to “buffer the landscape” from droughts and other extreme events.

(Published under Creative Commons from Mongabay-India. Read the original article here)