Climate Change & Anthropocene Extinction 30: Heavy breathing tropical forests under record heat

Today the WMO announced that the atmospheric CO2 concentration last year rose at a record high speed: +3.3 ppm – jumping from 400.0 ppm in 2015 to 403.3 in 2016. The annual average rise is close to 2 ppm.

A few days earlier NASA scientists had explained why the global CO2 rise has suddenly rapidly accelerated: rainforests across Earth’s tropics, suffering unprecedented heat and drought, and exhaling a massive amount of CO2 (9.2 billion tonnes) – adding over 50 percent to the global fossil fuelled economy:

tropical forests CO2 source climate change
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Climate Change & Anthropocene Extinction 29: Last straw Madagascar bamboo lemur drying out

When you’re looking at the effects of climate change on the forests of Africa, you may be inclined to overlook Madagascar, the continent’s largest island. But especially when biodiversity is your concern, it deserves special attention.

In fact Madagascar has more endemic-only tree species than any other African country. And although the Congo Basin – Africa’s tropical rainforest heartland – is rich in iconic primates like the chimpanzee, bonobo and gorilla, Madagascar is the single home of a uniquely separate clade of primates called ‘lemurs’, which evolved independently from monkeys and apes.

Madagascar bamboo lemur threatened climate change
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Climate Change & Anthropocene Extinction 28: If the Amazon goes, so may Africa’s rainforests

The Congolese rainforests are the world’s second largest remaining tropical rainforest expanse and a 60 gigatonne carbon store. Although climate models have a hard time predicting rainfall changes over the Congo Basin and despite a multi-decade drying trend, these forests in the heartland of tropical Africa are generally thought to be relatively resilient to the effects of climate change – at least when compared to the Amazon, a well-researched climate tipping point.

But ironically the possible large-scale drying and disappearance of the Amazon rainforest might also be the climatic Achilles’ heel of the Congolese rainforests.

Drying rainforests of Amazon and Congo due to global climate change, according to NOAA NCEP
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Climate Change & Anthropocene Extinction 27: Africa is warming fast, but what about Congo Basin?

21st century climate change affects the entire globe: every ecosystem, every mountain range, all the glaciers, all the land, the oceans. But of all continents it’s often said that Africa will face the biggest impacts.

African climate change is far from a uniform process though. Large geographical differences occur across the continent, that together form a pattern, as for all the African regions changes in temperature and precipitation are directly influenced by changes in the general circulation of the atmosphere.

While it’s clear that some regions will get really dry, others may get really wet, and some may warm faster than others; it is climate impacts on Africa’s tropical heartland that are perhaps most uncertain, as different climate models have a hard time capturing both the present and future convective precipitation that the Congolese rainforests depend on – rainforests that in turn are hugely important for the health of our planet as they are Africa’s densest biodiversity hotspot and a carbon store weighing in at a 60 gigatonne significance to the global climate system.

African forest elephants & Congolese climate change
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Climate Change & Anthropocene Extinction 26: Congolese rainforests store twice as much carbon

A new study, published earlier this year in Nature, shows that the Congolese rainforests store far more carbon than previously thought: over 60 billion tonnes, about half of which in the living biomass of the forest trees, and the other half as shallow peat – mainly in the ‘Cuvette Central’, a huge forested wetland in its centre:

Congo rainforest carbon store twice as large, Nature study shows

If this terrestrial carbon store were cut down, burned, drained, or otherwise oxidised (for instance through increasing droughts in the Congo Basin) that would equate to emissions of approximately 220 billion tonnes of CO2. And that makes protection of Africa’s densest biodiversity hotspot of immediate significance for the stability of the global climate system.

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Climate Change & Anthropocene Extinction 25: Congo rainforest shows drying trend – and degradation

The climate over the Congolese rainforests (in the central tropics of Africa) seems to show a drying trend over the last four decades. And although this deviation is smaller than multi-annual variation, the average decline in precipitation does lead to forest degradation in the world’s second-largest remaining tropical rainforest.

Climate change over Congo rainforests: declining precipitation trend
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Climate Change & Anthropocene Extinction 24: Insects Germany declined 76% in just 27 years(!)

The numbers of flying insects in nature reserves throughout Germany show a staggering decline. Taken on average over the months of April to October between 1989 and 2016 insect numbers declined 76%. In mid-summer measurements show an even more rapid decline, with insect numbers now 82% down compared to just 27 years ago.

This we learn from a study by a group of German and Dutch ecologists of Radboud University and the Entomological Society Krefeld that was published yesterday.

Anthropocene Extinction graph: insect decline Germany
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Climate Change & Anthropocene Extinction 23: Amazon ‘tipping point’ is a sliding process, from +1C

In this article we try to quantify the Amazon rainforest climate tipping point, based on available scientific literature. We conclude there’s no real basin-wide threshold temperature to activate the forest-killing biome switch. Rather it seems to be a sliding process, that we are already largely committed to under current CO2 concentrations.

The most rapid warming-induced die-back of the Amazon rainforest probably occurs at a global average temperature rise from 1 to 3 degrees Celsius above the pre-industrial climate. The vegetation effect is delayed, initially masking part of the damage. Yes, that’s sadly yet more climate inertia

Amazon rainforest climate tipping point
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Climate Change & Anthropocene Extinction 22: Central American rainforests may also dry out – and die

In our previous article we saw how climate change dries out the Amazon rainforest from the South – killing all remaining rainforest in Bolivia and Paraguay, and most in Peru and Brazil.

So, we wonder, what’s going on with the rainforests further to the North? Are these more resilient? Well, the northern margin of the Amazon basin: perhaps – but Central America: probably not – a recent study says.

Climate change drought in Central America
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Climate Change & Anthropocene Extinction 21: Amazon rainforest die-off starts in the South, models show

People who follow climate science will likely be well aware that the Amazon rainforest is particularly vulnerable to anthropogenic climate change – as the basin becomes increasingly prone to droughts under rising global temperatures. Much of the Amazon ecosystem, the largest terrestrial hotspot of biodiversity, may collapse, flipping to a barren savanna-like state (cerrado grassland and caatinga semi-desert).

Regulars of Bitsofscience.org may also be able to explain why this biome switch might happen and describe a worrying geographical phenomenon in which the Amazon rainforest is essentially being swiped off the South American continent into the Caribbean Sea – climate extinction on a truly massive scale, as the below image illustrates:

Amazon rainforest climate change model prediction
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