Rocky outcrops in the Western Ghats of India harbour a unique ecosystem in the form of freshwater rockpools where organisms adapt to survive in extreme weather. Photo: Sameer Padhye
Dry up. Wait for the rain. Soak in and bloom. Hold out and fade. Dry up. Wait. Soak in and bloom.
It’s a fast-paced life in the pools dotted across India’s rocky outcrops. The circle of life repeats year after year, dependent on the tiniest of changes, where some organisms live and die as water swells and dries up, and others slurp up enough until the next monsoon comes. Some go to extreme lengths and evolve to not even need water to survive — or keep an arsenal of eggs and spores saved for a rainy day.
Rocky outcrops are born due to time and erosion. They form when softer parts of the landscape erode over millions of years, leaving behind a hard core of parent rock, often protruding above the surface of the surrounding land. They can contain rock pools that last seasonally or throughout the year. Found on all continents, in most climate zones and vegetation types, they act as both refuge and archive for an ecosystem’s denizens, storing the history of a particular landscape, and even giving proof that Australia was once a large rainforest.
Rocky outcrops are a type of small natural feature: spatially diminutive natural entities with highly variable environmental conditions, and which often harbour a unique assemblage of organisms. Scientists often compare them to keystone species, since they have a larger effect on ecosystems than their size or abundance would suggest. Like frogs.
Biologist Malcolm Hunter, in a 2017 paper, had a better analogy. “Small natural features are an example of what can be termed ‘The Frodo Effect,'” he wrote. “In the ‘Lord of the Rings,’ the small and unassuming hobbit Frodo has more strength than any of his larger peers and saves Middle Earth with his brave actions. Gandalf and the rest of the fellowship of the ring go to great ends to protect him, because they know this.”
Other examples of such features include desert springs, bat caves, vegetation bordering agricultural fields and large old trees. While each of these harbours its own, unique environmental fluxes, rocky outcrops perhaps have the bigger flex on them.
“Rocky outcrops have a different microclimate than the surrounding regions, which is highly dynamic,” says Mihir Kulkarni1, a postdoctoral researcher at the Centre for Cellular and Molecular Biology, Hyderabad. “For example, the temperature experienced in a single day can range between 20º to around 50º C. This creates a challenging environment, which can largely ‘filter out’ species that disperse to these habitats.”
The microenvironment of the rocky plateaus in fact tends to extremes, from xeric, or water-deprived, to water-logged. While the conventional term uses the word ‘rocky’, outcrops can be soil-covered plateaus as well. The nature of the surroundings of the plateaus, the altitude they are at, rainfall, exposure to sunlight and chemical composition of the plateau itself affect the diversity of life found on them, giving rise to synonyms like “terrestrial habitat islands” and the microhabitats on them as “islands upon islands”.
Gradients in environmental variables exist even at small scales (on a single outcrop), according to Kulkarni.
In India, the habitat is represented in many ways. Aparna Watve, a Pune-based professor who has worked extensively on the flora of rocky outcrops, has written, “Large monolithic inselbergs and koppjes are common in South India. Cliffs are the dominant outcrop type in the mountainous regions. Rocky plateaus of basalt and laterite present in Western Maharashtra are of high botanical value due to presence of endemic plants.”
There is no data available on the total area that rocky outcrops cover in India. The lateritic plateau of Kas, a UNESCO World Heritage site, in the northern Western Ghats is perhaps one of the best-known rocky outcrops in the country. Its post-monsoon flowering draws heavy tourist footfall, and many of the delicate plants seen are found nowhere else. Carnivorous plants are especially abundant in Kas, since the extreme variability of nutritional sources in the soils has pushed them to seek food by other methods.
“These habitats hold water only for a few months of the year and hence organisms capable of surviving in such conditions can thrive in these habitats. This results in the evolution of new species adapted to rock pools in many cases, making the diversity unique,” Sameer Padhye, a Pune-based scientist who has studied the diversity of invertebrate life in rocky outcrops in the Western Ghats, says.
The Indian monsoon is key to the uniqueness of this biodiversity, since it lasts longer here than most other places in the world. The ‘hydroregime’, which lasts for months as opposed to just a few weeks in temperate zones, means that rock pools retain water for longer and thus ensure a longer flourishing period for their inhabitants.
Shruti Paripatyadar, a Pune-based entomologist who did her PhD on the natural history of aquatic bugs in Maharashtra, says that the longer inundation period is also why insects have diversified in these outcrops.
“These habitats are significantly different from rock pools that occur elsewhere in the world because of their large size and hydroperiod (the amount of time water persists in a pool). The clearly marked wet season due to the Indian monsoon contributes to the stability of these habitats, which is rare in other such habitats. This stability is probably the reason that these habitats harbour such a diverse invertebrate community.”
Paripatyadar and her colleagues have the results that prove this: 13 new species of micro-crustaceans, some of which are found only in a single rock pool. If this wasn’t surprising enough, she also found flightless individuals of insect species that usually have wings.
“Depending on the permanence of an aquatic habitat, aquatic bugs can have flightless individuals in a population, because there is a trade-off between the ability to fly to new habitats and reproductive success in the current habitats,” she says. “The energy potentially required for functioning wings is redirected to reproduction and hence in stable, perennial habitats, adults are often incapable of flight. But the occurrence of flightless individuals in temporary pools was surprising.”
In some species, 100% of the individuals encountered appeared to be flightless. Paripatyadar suspects that the relatively stable nature of these habitats might be responsible for many species having flightless populations.
Scientists have better-studied the flora of rocky outcrops in India, but overall, it’s not a comprehensive database. “Global datasets on biodiversity of rocky outcrops largely comprise information from the Americas, Africa, Europe and Australia. Data from Indian systems is conspicuously absent, primarily due to scarcity of studies,” says Kulkarni.
Lack of data is only one bugbear. Ignorance is another.
“Despite harbouring high biodiversity, such temporary pools are globally threatened, and more so in India,” according to Kulkarni. “Lack of data on their biota coupled with near absence of public awareness makes these habitats truly ‘invisible’ to conservation agencies.”
Watve says that they also get categorised as ‘wastelands’ due to their apparent barrenness. In a 2013 review of rocky plateaus in Maharashtra, she wrote that only a handful of rocky outcrops are safe because they happen to be in protected areas or are inaccessible.
“The 2010 Wastelands Atlas of India by the National Remote Sensing Centre and Ministry of Rural Development showed extensive … ‘barren rocky/stony waste areas’ in Kolhapur, Pune, Satara, Ratnagiri and Sindhudurg districts, which in reality are rocky plateaus with high biodiversity value,” she explained. “The wasteland status has been easily exploited for acquiring rocky plateaus for mining, wind farms and infrastructure projects throughout the study area.”
Tourism does not help the cause much either. “At Kas, the plateau fencing was put up to stop people from driving their vehicles in the wildflower blooms for ‘perfect photos’,” Kulkarni says.
Similar temporary habitats in European regions have received legislative protection, including through the Mediterranean Habitats Directive and the European Pond Conservation Network. Habitats and species, such as vernal pools and fairy shrimp, in the US are federally protected. But lack of comprehensive data on biota of Indian pools makes any such conservation action difficult in the subcontinent.
Paripatyadar also points out a long-standing scientific bias due to lack of ‘charisma’. “From the point of view of conservation, it is very difficult to convince policy makers to conserve these habitats or successfully get funding for continuing the research due to the absence of species which are traditionally considered ‘attractive’,” she argues.
These unique habitats, like others, will also suffer due to the effects of climate change. Padhye, who has studied rocky outcrops for nearly a decade now, says that even if the flora and fauna of rock pools is used to change, they still have a limit to what they can tolerate.
“Climate change is affecting all aquatic systems. All organisms have an optimum range of environmental conditions (e.g. temperature) in which they can thrive.”
It is, effectively, a race against time.
Renuka Kulkarni is a science writer based in Pune, India, and is currently pursuing a PhD in political ecology.
No relation to the author↩