Hindu Notes from General Studies-01

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Fish adapt to climate change

News

• Scientists have studied how fish adapt to rapid changes in the surrounding freshwater environment to understand how the marine life may respond to climate change.

Findings

• Freshwater biodiversity is rapidly declining worldwide, and nature-based solutions which increase the resilience of ecological communities are becoming increasingly important in helping communities prepare for the unavoidable effects of climate change.
• Researchers varied the water current and depth in a simulated river with obstacles, and found that fish were able to rapidly adapt to the changes when alone and also when in groups.
• The findings suggest that cues initiated by obstacles in the flow can be detected by fish to find energetically-beneficial places in the flow even under extreme and rapid environmental change.
• The concept of observing fish in simulated rivers as individuals or in groups is not unusual, but the effects of rapid environmental variations, such as quickly changing water depths due to hydropower plant operations or a flash flood remain largely unknown.
• Fish sense their surroundings using the biological lateral line, which consists of canals and tiny hair-like structures which are sensitive to minute changes in the water motion and pressure near the fish’s body.
• The researchers observed that both individual fish and groups of fish reacted to the changing flow conditions in very clear ways and wondered if their natural flow sensing abilities were guiding their ability to cope with the stressors.
• Understanding how a fish’s advanced sensing system help them react to rapid changes in the flow environment will help scientists develop new designs for nature-based solutions to improve climate change resilience.

Urban areas are cooler than non-urban areas during heat waves

News

• A study of 89 urban areas in India has found that though there is an absolute increase in temperature during heat waves in both urban and non-urban areas, the urban areas are relatively cooler than the surrounding non-urban areas.
• At 1.94°C, the absolute increase in temperature during the day in non-urban areas during a heat wave was significantly higher than in urban areas (0.14°C).

Findings

• According to the analysis, urban areas were found to be relatively cooler than the surrounding non-urban areas during heat waves. At 44.5°C, the non-urban areas were warmer than urban areas (43.7°C). However, during the night, all urban areas were hotter than the surrounding non-urban areas.
• The urban areas witness less temperature increase during heat waves compared with non-urban areas due to significantly higher tree cover and more number of water bodies.
• In contrast, a majority of non-urban areas are located in agriculture-dominated regions. In non-urban areas, the vegetation cover in the form of crops and soil moisture from cropland irrigation decline sharply after crops are harvested and well before the onset of heat waves during summer.
• The urban areas, on the other hand, have perennial vegetation in the form of tree cover and lawns, and more number of water bodies, which help in keeping the urban areas relatively cooler than non-urban areas.
• The land surface temperature was estimated by analysing satellite data collected between 2003 and 2016. Between 1951 and 2016, a majority of urban areas experienced about five hot days and nights per year.
• About 44% of urban areas showed an increase in frequency of hot days while 34% showed a significant decline in frequency of hot days.

Hindu Notes from General Studies-03

Protected areas matter to bumphead parrotfish

News

• The survival of the threatened bumphead parrotfish in the Andaman and Nicobar Islands hinges on the persistence of coral reefs and presence of marine protected areas.
• Implementing fishing regulations could help its population bounce back.

Beyond News

• Bumpheads are the world’s largest parrot fish. Ramming its enormous green head against corals to dislodge them, a single bumphead can nibble up to five tonnes of coral every year.
• Though seemingly destructive, this activity promotes coral growth and keeps reef ecosystems healthy.
• Live coral cover and the presence of marine protected areas where fishing is banned emerged as crucial factors for bumphead presence.
• To supplement this information with local knowledge, the team also conducted 99 interviews with fishermen in the South and Middle Andaman islands and Central Nicobar.
• Most fishers were aware of the presence of bumpheads in their waters; and all fishermen in Central Nicobar and Middle Andaman had seen the fish feeding and aggregating (bumpheads tend to aggregate in numbers larger than 10). Most fishers had hunted the fish all their lives, using hand-held wooden spears or harpoons.

Ooty’s muon detection facility measures potential of thundercloud

News

• For the first time in the world, researchers at the GRAPES-3 muon telescope facility in Ooty have measured the electrical potential, size and height of a thundercloud that passed overhead.
• At 1.3 gigavolts (GV), this cloud had 10 times higher potential than the previous record in a cloud. This is not because clouds with such high potentials are a rarity, but rather, because the methods of detection have not been successful so far.

Beyond News

• Clouds have negative charges along their lower side and positive charges on top and can be several kilometres thick. If balloons are used to measure the potential difference between the top and bottom, they will take hours to traverse the distance. Unfortunately, thunderstorms last only for about 15-20 minutes, and this method fails.
• Muons and other particles are produced when cosmic rays bombard air particles surrounding the earth. The muons produced can have positive or negative charge. When a positively charged muon falls through a cloud, it loses energy. If its energy falls below 1 giga electron volt (GeV), which is the threshold of detection of the GRAPES-3 muon telescope, it goes undetected.
• On the contrary, a negatively charged muon gains energy when falling through the cloud and gets detected. Since there are more positive than negative muons produced in nature, the two effects don’t cancel out, and a net change in intensity is detected.
• Using a computer simulation and the observed muon intensity variations, the group worked out the relationship with the electric potential of the cloud. They calculated that the potential of the cloud they were studying was approximately 1.3 GV.
• Learning about the properties of thunderclouds can be useful in navigation of aircraft and preventing short circuits. This serendipitous discovery might provide the means to making headway in this direction.

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