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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Climate Change & Anthropocene Extinction 20: Amazon tree transpiration crucial to keep rainforest wet

The individual trees in the Amazon rainforest play a crucial role in keeping the rainforest intact. Not just because the trees together create the forest, but also because – together – they create the climate (through something called the shallow moisture convection pump).

Take home message: in order to preserve the Amazon, deforestation really has to stop completely. A ‘meeting in the middle’ compromise does not work – as (amplified by global climate change) that promotes devastating droughts in the remaining part of the forest.

Amazon rainforest - artist impression of deforestation, WWF ad
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Climate Change & Anthropocene Extinction 19: Earth has 60,065 tree species, almost half threatened

When we think of the Holocene-Anthropocene Mass Extinction we may think of coral reefs, birds, amphibians and iconic mammal species – essentially following the IUCN Red List.

But it really is time we started to take a closer look at trees. Their total biodiversity is far larger – and if we can make a blunt statement: it’s also more important.

Tree biodiversity per biome (ecozone) on Earth
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Climate Change & Anthropocene Extinction 18: Widespread effects ‘biodiversity redistribution’ unaccounted

We can all imagine that climate change-driven migration of species will have global consequences. But what do the actual effects look like – and how do these feed back on ecology, climate and human societies?

effects of 'biodiversity redistribution' (climate change-driven species migration)
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Climate Change & Anthropocene Extinction 17: These 6 killers still bigger drivers than warming – IUCN study

An analysis of IUCN’s Red List of endangered species places 10 drivers of the Holocene-Anthropocene Mass Extinction in order of severity. It concludes that classical environmental threats like deforestation, hunting and overfishing – in 2016 – still top the list of biodiversity killers.

Anthropogenic climate change is currently affecting 19 percent of species that are listed as threatened or near-threatened – making it the 7th extinction driver. (Stating the obvious: this position will change, as temperatures continue to rise.)

Current drivers of the Holocene-Anthropocene Mass Extinction - IUCN study
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Climate Change & Anthropocene Extinction 16: Land use & warming exert same stress on tropical biodiversity

Anthropogenic climate change and land use change in the form of agricultural expansion (‘habitat conversion’ – a sweet description for deforestation) act as synergistic drivers of biodiversity loss – in a Costa Rican environmental experiment – literally drying out the natural diversity of species, bird species at least.

Biodiversity loss from drought and expansion of agriculture
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