These migrants need attention, too

LOSING GROUND Important fish species such as mackerel have been, over the years, forced to extend theirrange owing to global warming. Picture shows the Indian mackerel. Photo: CC-BY-ND 2.0: BBM EXPLORER; FLICKR.COM  

Our fish are moving north.

Until about the mid-1980s, important fish species such as mackerel and oil sardines used to be present no further north than the Malabar upwelling zone off the Kerala coast. Because of global warming, sea surface temperatures along India’s west coast rose by 0.6 degrees Celsius over 1967-2007, according to the Kerala State Action Plan on Climate Change. Consequently, these fish species began to find the ocean waters further north also rather salubrious. In the last thirty years, the northern boundary of their range — the geographical area over which any given species is to be found — has extended a staggering 650 kilometres. Having moved beyond Karnataka and Maharashtra, they can now be found in waters off Gujarat. Off India’s eastern coast too, the mackerel’s range has shifted north, from the Andhra coast earlier to waters off parts of West Bengal presently.

This shift in the range of species is also taking place in India’s rivers. Along the Ganga for instance, four species of warm water fish can now be found swimming further north, up to Haridwar, as the average minimum temperatures of river waters in this stretch had warmed by 1.5 degrees Celsius by 2009 over the 1970-1986 average.

Shifts or extensions in species’ range because of global warming are occurring with innumerable species in every region, terrain and ecosystem in India. Rising temperatures are the most obvious cause, but changing rainfall patterns is also a factor. And in some cases, a species itself may not need to move but is forced to shift because its food/prey may have. This phenomenon is not unique to India. Meta-surveys of published papers covering hundreds of marine and land-based species the world over have found that, as the globe warms, three-quarters of all marine species studied have shifted their ranges poleward, as have half of all land-based species. Many are also creeping up mountain slopes.

Moving treelines

In fact, as the Indian Himalayas have warmed by 1.5 degrees Celsius on average in the past few decades, a number of species now find lower altitudes too warm for comfort. The case of Himachali apples, which no longer thrive in the lower Kullu Valley, is the most well-known, but scarcely the only one. The treeline in Uttarakhand has itself moved higher by over a thousand feet since the 1970s. In the eastern Himalayas, innumerable species — of reptiles, butterflies, birds, deer, bees — have all had to shift higher. One study alone from Sikkim listed twenty-five such species.

Species in India also suffer other effects of global warming: heat stress, ocean acidification, greater pest attacks, and droughts. But no phenomenon captures the chaos it is causing in the natural world more than the changing timing of annual lifecycle events – or phenology – of plants and animals. Changes studied elsewhere include the timing of first flowering, bud emergence, birds nesting, the timings of frogs breeding, etc.

Scientists at the G.B. Pant Institute in Almora examined long-term records of the flowering dates of rhododendrons since 1893; they are now flowering earlier by over forty days. They also found a clear correlation of this phenomenon with rising temperatures. Numerous species across the Himalayan range have been similarly affected. One has heard of similar changed timings of flowering or of budburst happening with mangoes in my village in coastal Karnataka, figs in Manipal, chironji (Buchanania lanzan) in Orissa, coffee in Kerala. And as the ocean waters off Chennai have warmed, two fish species have shifted their annual spawning to the period between October and March. The other months have become too warm.

Shifts in range or in the timing of lifecycle events are climate change adaptations by species. But it would be optimistic to assume they can all cope. When timings change in plants, it creates problems for other species dependent on them for food. When species shift, northward or higher, not all species in an ecosystem may move, and the interconnectedness that has evolved over decades gets disrupted. And in their sometimes desperate effort to shift, species may be hindered by urban growth. Or by natural barriers: what happens as sea waters warm, one expert asked, to the famous Bombay duck (bombil), whose northern boundary is landlocked Gujarat? Extinctions of mountain-restricted frogs and toad species due to global warming have occurred in Europe as they had nowhere higher to climb. A number of studies in India have voiced concern about extinctions here too in the not too distant future affecting endemic species and alpine plants at the top of mountain ecosystems, forest species of pine and sal in central India, the Nilgiri tahr in the montane forests down South among others.

To briefly conclude, the crisis of global warming is rendered qualitatively different and gains even greater urgency if one considers its impacts on other species. With so much havoc already occurring across ecosystems at current levels — 0.9 degrees Celsius — of average warming, one shudders to think what further warming might imply for an untold number of species in India.

And in turn for us humans — the livelihoods of millions of people depend on the location and well-being of other species. How marginal farmers, fisherpeople and other communities in different parts of India are being affected by impact on other species merits much more detailed investigation. As the world heads towards the >crucial COP21 negotiations in Paris in December, one can only hope that political elites are keeping an ear out for what other species are trying to tell us about global warming as they struggle to cope. Life is an interconnected web, and we ignore what they tell us at our peril.

( Nagraj Adve is a member of the India Climate Justice collective. He works and writes on issues related to global warming. )

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Printable version | Sep 15, 2021 1:48:18 PM |

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