We are living through an unexpectedly bountiful renaissance in some marine ecosystems

See Right on plastics and PCBs, wrong on acidification: The BBC's Blue Planet II is superb, but got a few things wrong by Matt Ridley. Excerpt:

"It was good, too, to hear Attenborough’s recognition, rare on the BBC, that we are living through an unexpectedly bountiful renaissance in some marine ecosystems. Too often we are told only the bad news. The last episode featured the recovery of turtles, as well as the resurgent herring, killer whales and humpback whales of Norway, and the vast concentrations of sperm whales now being seen for the first time since the era of Moby Dick. Many populations of sperm, right, grey, bowhead, fin, blue and humpback whales are now high again, and rising at 5 to 10 per cent a year, something I never dreamt would happen in my lifetime.

The series could have made the same point about the penguins, fur seals and elephant seals of South Georgia, an island denuded of almost all wildlife about 75 years ago, but now once again teeming. Or about walruses, an Arctic species that has rebounded after centuries of exploitation. When I first visited Spitsbergen in the 1970s there were about 100 walruses there. Today there are about 4,000 and the population is still increasing rapidly.

Walruses were brought to the brink of extinction in Svalbard (Norway) during 350 years of unregulated harvesting. They became protected in 1952, when few remained. During the first 30 years of protection, approximately 100 animals became established within the archipelago, most of which likely came from Franz Josef Land, to the east. A marked recovery has taken place since then. This study reports the results of a photographic aerial survey flown in summer 2012, covering all current and historical haul-out sites for walruses in Svalbard. It provides updates regarding the increasing numbers of: (1) landbased haul-out sites (from 78 in 2006 to 91 in 2012); (2) occupied sites (from 17 in 2006 to 24 in the 2012 survey); (3) sites with mother-calf pairs (which increased from a single site with a single small calf in 2006 to 10 sites with a total of 57 small calves in 2012) and (4) a 48% increase in abundance in the six-year period between the two surveys to 3886 (confidence interval 3553-4262) animals, including animals in the water at the time of the survey. Future environmental change might reduce benthic production in the Arctic, reducing the prey-base for walruses, and also impact walruses directly via declines in their sea-ice breeding habitat. But, currently the Svalbard walrus population is growing at a rate that matches the theoretical maximum rate of growth that has been calculated for recovering walrus populations under favourable environmental conditions with no food limitations.
Walruses recovering after 60+ years of protection in Svalbard, Norway (PDF Download Available). Available from: https://www.researchgate.net/publication/266713764_Walruses_recovering_after_60_years_of_protection_in_Svalbard_Norway [accessed Dec 12 2017].

So it was naughty of Blue Planet II, in showing a sequence in which a mother and calf walrus desperately try to find a bit of ice big enough to bear their weight but not already occupied by other walruses, to imply that this was evidence of climate change threatening a species with extinction. Most of the ice in the Arctic Ocean disappears each summer and reappears each winter. Walruses have hauled out on shore, or on what’s left of the ice at that season, forever. The main thing that has changed is that there are now more walruses, and more polar bears feasting on them, throughout the Arctic.

So the climate change obsession is still sometimes getting in the way of telling the truth. The most dishonest sequence in the series was when Attenborough watched shells dissolving in a tank of acid, to a soundtrack of fizzing noises, and was told by Professor Chris Langdon that although this was “more dramatic than what’s happening in the oceans”, nonetheless “the shells and the reefs are really truly dissolving”.

This is highly misleading in several different ways. Was it carbonic acid, or another acid? The reduction in alkalinity will get nowhere near neutral, let alone actual acidity, even by the end of the 22nd century, so “dissolving” is false, let alone happening now. The changes in ocean pH expected even by the end of this century are minuscule compared with what was shown in that tank, and by comparison with the daily and seasonal changes that an average reef experiences. (Coral bleaching, a different issue, is more serious, but more temporary.)

A 2010 analysis of 372 studies of 44 different marine species found that the world’s marine fauna is “more resistant to ocean acidification than suggested by pessimistic predictions” and that it “may not be the widespread problem conjured into the 21st century”:

Ocean acidification has been proposed to pose a major threat for marine organisms, particularly shell-forming and calcifying organisms. Here we show, on the basis of meta-analysis of available experimental assessments, differences in organism responses to elevated pCO2 and propose that marine biota may be more resistant to ocean acidification than expected. Calcification is most sensitive to ocean acidification while it is questionable if marine functional diversity is impacted significantly along the ranges of acidification predicted for the 21st century. Active biological processes and small-scale temporal and spatial variability in ocean pH may render marine biota far more resistant to ocean acidification than hitherto believed.

And recent work has established that corals’ ability to make skeletons is “largely independent of changes in seawater carbonate chemistry, and hence ocean acidification...the relevance of their commonly reported finding of reduced coral calcification with reduced seawater pH must now be questioned”. Indeed, one study found that calcifying plankton “respond positively to acidification with CO₂enrichment”,

As a result, cell growth and cellular calcification of E. huxleyi were strongly damaged by acidification by HCl, but not by acidification by CO2 enrichment...The present study clearly showed that the coccolithophore, E. huxleyi, has an ability to respond positively to acidification with CO2 enrichment, but not just acidification.

another that the growth rate of corals also increases with higher carbon dioxide up to 600 parts per mllion and concluded:

Furthermore, the warming projected by the Intergovernmental Panel on Climate Change for the end of the twenty-first century caused a fivefold decrease in the rate of coral calcification, while the acidification projected for the same interval had no statistically significant impact on the calcification rate—suggesting that ocean warming poses a more immediate threat than acidification for this important coral species.

The producers of Blue Planet II claim every word of the commentary was based on solid scientific evidence. Not in this case. In a magnificent series, they got that one wrong."