Study Indicates Global Warming Could Reduce Biodiversity In Tropics

Study Indicates Global Warming Could Reduce Biodiversity In Tropics

Published in the journal Current Biology, the study estimates that marine biodiversity tends to increase until the average surface temperature of the ocean reaches about 65 degrees Fahrenheit, beyond which that diversity slowly declines
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Study Indicates Global Warming Could Reduce Biodiversity In TropicsMarine life that could travel considerable distances likely migrated north or south from the tropics during periods of extreme heat, said co-author Will Gearty
Highlights
  • For the study, the researchers went back about 145 million years
  • They compiled estimated temperatures and fossil records of molluscs
  • They got temperature-diversity relationship across 10 geologic intervals

Washington: New research by the University of Nebraska-Lincoln suggests that temperature can largely explain why the greatest variety of aquatic life resides in the tropics but also why it has not always and, amid record-fast global warming, soon may not again. The bulging, equator-belted midsection of Earth currently teems with a greater diversity of life than anywhere else – a biodiversity that generally wanes when moving from the tropics to the mid-latitudes and the mid-latitudes to the poles. Published in the journal Current Biology, the study estimates that marine biodiversity tends to increase until the average surface temperature of the ocean reaches about 65 degrees Fahrenheit, beyond which that diversity slowly declines.

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During intervals of Earth’s history when the maximum surface temperature was lower than 80 degrees Fahrenheit, the greatest biodiversity was found around the equator, the study concluded. But when that maximum exceeded 80 degrees, marine biodiversity ebbed in the tropics, where those highest temperatures would have manifested, while peaking in waters at the mid-latitudes and the poles. Marine life that could travel considerable distances likely migrated north or south from the tropics during periods of extreme heat, said co-author Will Gearty, a postdoctoral researcher of biological sciences at Nebraska.

Stationary or slower-moving animals, such as sponges and sea stars, may have instead faced extinction.

People have always theorized that the tropics are a cradle of diversity — that it pops up and then is protected there, Will Gearty said.

“There’s also this idea that … there’s lots of migration toward the tropics, but not away from it. All of that centres around the idea that the highest diversity will always be in the tropics. And that’s not what we see as we go back in time.”

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Will Gearty, Yale’s Thomas Boag and Stanford’s Richard Stockey went back about 145 million years, compiling estimated temperatures and fossil records of molluscs — snails, clams, cephalopods and the like — from 24 horizontal bands of Earth that were equal in surface area. The trio chose mollusc records for multiple reasons: They live (and lived) around the globe, in large enough numbers to accommodate statistical analyses, with hard enough shells to yield identifiable fossils, with enough variation that their diversity trends might generalize to fish, corals, crustaceans and an array of other marine animals. That data allowed the team to derive the temperature-diversity relationship across 10 geologic intervals that covered most of the elapsed time from the Cretaceous period through the modern-day.

Temperature seems to account for a lot of the trend that we see in the fossil record, Will Gearty said.

“There are certainly other factors, but this seems to be the first-order predictor of what’s going on.”

To investigate why temperature might be so influential and predictive, Richard Stockey took the lead in developing a mathematical model. The model accounts for the fact that higher temperatures generally increase the amount of energy in an ecosystem, theoretically raising the ceiling on the biodiversity an ecosystem can sustain, at least to a point. But it also factors in metabolism and the small matter of oxygen, which, by dissolving in water, makes aquatic life possible in the first place. Colder waters dissolve more oxygen, meaning that elevated temperatures naturally reduce the amount available to marine life and, by extension, potentially limit the biodiversity an ecosystem can support. Higher temperatures also raise the metabolic demands of organisms, increasing the minimum oxygen needed to sustain active marine animals.

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That means you require more oxygen in warmer waters, Will Gearty said.

“And if the amount of oxygen available is not satisfying that increase in metabolism, you won’t survive in that environment. So, to survive, you’ll need to move to another environment where the temperature is lower.”

The team applied its model to numerous marine species with varying metabolisms. As expected, metabolism influenced how the population of a given species would respond to a rise in temperature, along with the temperature threshold beyond which that population would decline. When the researchers averaged the effects of metabolism and oxygen availability across those species, they discovered that the resulting temperature-diversity relationship resembled — and, in doing so, supported — the one they derived from the fossil record.

It shows a similar trend of this (biodiversity) increase and then decreases, Will Gearty said.

“After many a day at the whiteboard just trying to figure out how to make it work, it all just came together very nicely at the end — you know, a nice little bow on top.”

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Collectively, the study indicates that human-driven global warming could hit the inhabitants of tropical waters especially hard. The average surface temperature of tropical waters could jump by as many as 6 degrees Fahrenheit by the year 2300, according to one projection. And according to the fossil records analyzed for the study, similar temperature increases during the past 145 million years have sometimes permanently driven mollusc species from tropical waters. There are worrying signs that the expected trend is already underway, Will Gearty said.

Though the team had difficulty narrowing down the projected magnitude of the decline in biodiversity, Will Gearty said the worst-case projection called for the tropics losing up to 50 per cent of their marine species by 2300. Some of the loss will take the form of migration. Yet the warming could spell doom for, say, corals and the thousands of marine species that they support, he said, as seen in the oft-fatal bleaching of the Great Barrier Reef off the coast of Australia.

This (biodiversity loss) is already happening, and it will only keep happening unless we do something, Will Gearty said.

“We can’t really take back the buildup of carbon dioxide (in the atmosphere) that’s already happened, so it’s going to keep happening for some amount of time. But it’s up to us to determine how long until it’ll stop.”

Also Read: India And United Kingdom Deepen Work To Combat Climate Change By 2030

(This story has not been edited by NDTV staff and is published from a syndicated feed.)

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World

17,91,56,496Cases
5,81,68,051Active
11,71,06,212Recovered
38,82,233Deaths
Coronavirus has spread to 193 countries. The total confirmed cases worldwide are 17,91,56,496 and 38,82,233 have died; 5,81,68,051 are active cases and 11,71,06,212 have recovered as on June 23, 2021 at 3:45 am.

India

3,00,28,709 50,848Cases
6,43,19419,327Active
2,89,94,855 68,817Recovered
3,90,660 1,358Deaths
In India, there are 3,00,28,709 confirmed cases including 3,90,660 deaths. The number of active cases is 6,43,194 and 2,89,94,855 have recovered as on June 23, 2021 at 2:30 am.

State Details

State Cases Active Recovered Deaths
Maharashtra

59,87,521 8,470

1,26,468 1,055

57,42,258 9,043

1,18,795 482

Kerala

28,29,460 12,617

1,00,881 746

27,16,284 11,730

12,295 141

Karnataka

28,15,029 3,709

1,18,615 4,541

26,62,250 8,111

34,164 139

Tamil Nadu

24,36,819 6,895

56,886 4,443

23,48,353 11,144

31,580 194

Andhra Pradesh

18,57,352 4,169

53,880 4,260

17,91,056 8,376

12,416 53

Uttar Pradesh

17,04,678 202

3,910 253

16,78,486 397

22,282 58

West Bengal

14,85,438 1,852

22,508 232

14,45,493 2,037

17,437 47

Delhi

14,32,778 397

1,918 78

14,05,927 467

24,933 8

Chhattisgarh

9,91,653 482

8,007 557

9,70,244 1,032

13,402 7

Rajasthan

9,51,393 137

2,388 303

9,40,101 437

8,904 3

Odisha

8,83,490 2,957

30,859 1,240

8,48,960 4,159

3,671 38

Gujarat

8,22,620 135

5,159 480

8,07,424 612

10,037 3

Madhya Pradesh

7,89,415 65

1,707 273

7,78,902 318

8,806 20

Haryana

7,67,726 146

2,200 137

7,56,231 263

9,295 20

Bihar

7,20,207 268

2,811 206

7,07,833 468

9,563 6

Telangana

6,15,574 1,175

16,640 606

5,95,348 1,771

3,586 10

Punjab

5,93,063 405

5,968 509

5,71,207 880

15,888 34

Assam

4,88,179 2,869

32,975 350

4,50,924 2,482

4,280 37

Jharkhand

3,44,775 110

1,417 72

3,38,256 180

5,102 2

Uttarakhand

3,38,978 171

2,896 68

3,29,030 231

7,052 8

Jammu And Kashmir

3,12,584 428

7,181 578

3,01,134 999

4,269 7

Himachal Pradesh

2,00,791 188

2,276 132

1,95,062 315

3,453 5

Goa

1,64,957 303

2,920 146

1,59,029 438

3,008 11

Puducherry

1,15,364 284

3,214 150

1,10,423 433

1,727 1

Manipur

64,993 575

9,214 84

54,714 649

1,065 10

Tripura

63,140 395

3,747 163

58,735 554

658 4

Chandigarh

61,467 23

278 33

60,383 56

806

Meghalaya

45,976 421

4,273 77

40,915 341

788 3

Arunachal Pradesh

33,664 289

2,548 9

30,956 279

160 1

Nagaland

24,438 64

1,757 87

22,204 149

477 2

Ladakh

19,871 33

360 5

19,309 38

202

Sikkim

19,458 137

2,430 18

16,732 152

296 3

Mizoram

18,409 430

4,424 197

13,900 233

85

Dadra And Nagar Haveli

10,520 4

61 1

10,455 3

4

Lakshadweep

9,504 33

315 4

9,142 36

47 1

Andaman And Nicobar Islands

7,425 10

103 6

7,195 4

127

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