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…
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.
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:
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.
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?
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.)
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.
Again, the use of a geographical approach (and here defining biodiversity as ‘biotic intactness’) shows the Holocene-Anthropocene Mass Extinction is progressing faster then generally thought – and ‘biodiversity safe limits’, however arbitrarily defined, have already been passed on most of the planet’s land surface.
Whether you focus on mammals, birds, reptiles or amphibians – land vertebrates are in rapid decline everywhere around us, illustrating a general decline of Life on Earth – and a prelude to the Holocene-Anthropocene Mass Extinction, that is being underestimated in speed and severity.
The reason of this underestimation: demography – the decline of species populations. This is not always counted in when assessing the global ecological crisis, but if you do, you get to see that the actual trend is much worse than most people think…