Claim: Global Warming Could Stress Tropical Plants

Cassowary Vicki Nunn / CC BY-SA

Guest essay by Eric Worrall

A recent Paleo climate study which demonstrated thriving tropical rainforests in a period when CO2 levels reached 2000ppm (5x today’s level) during the early Eocene has not discouraged UNSW climate scientists from predicting imminent doom.

Climate change threat to tropical plants

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02 JUL 2020   CAROLINE TANG 
Caroline Tang Media & Content (02) 9385 8809 caroline.tang@unsw.edu.au

Half of the world’s tropical plant species may struggle to germinate by 2070 because of global warming, a new UNSW study predicts.

Tropical plants closer to the equator are most at risk from climate change because it is expected to become too hot for many species to germinate in the next 50 years, UNSW researchers have found.

Their study analysed almost 10,000 records for more than 1300 species from the Kew Gardens’ global seed germination database. 

The research, published in the journal Global Ecology and Biogeography last month, was the first to look at the big picture impact of climate change on such a large number of plant species worldwide. 

Lead author Alex Sentinella, UNSW PhD researcher, said past research had found that animal species closer to the equator would be more at risk from climate change.

“The thought was that because tropical species come from a stable climate where it’s always warm, they can only cope with a narrow range of temperatures – whereas species from higher latitudes can cope with a larger range of temperatures because they come from places where the weather varies widely,” Mr Sentinella said. 

“However, this idea had never been tested for plants.

“Because climate change is a huge issue globally, we wanted to understand these patterns on a global scale and build upon the many studies on plants at an individual level in their environment.”

Read more: https://newsroom.unsw.edu.au/news/science-tech/climate-change-threat-tropical-plants

The abstract of the study;

Tropical plants do not have narrower temperature tolerances, but are more at risk from warming because they are close to their upper thermal limits

Alexander T. Sentinella, David I. Warton, William B. Sherwin, Catherine A. Offord, Angela T. Moles

Abstract

Aim

Tropical species are thought to be more susceptible to climate warming than are higher latitude species. This prediction is largely based on the assumption that tropical species can tolerate a narrower range of temperatures. While this prediction holds for some animal taxa, we do not yet know the latitudinal trends in temperature tolerance for plants. We aim to address this knowledge gap and establish if there is a global trend in plant warming risk.

Location

Global.

Time period

Present–2070.

Major taxa studied

Plants.

Methods

We used 9,737 records for 1,312 species from the Kew Gardens’ global germination database to quantify global patterns in germination temperature.

Results

We found no evidence for a latitudinal gradient in the breadth of temperatures at which plant species can germinate. However, tropical plants are predicted to face the greatest risk from climate warming, because they experience temperatures closer to their upper germination limits. By 2070, over half (79/142) of tropical plant species are predicted to experience temperatures exceeding their optimum germination temperatures, with some even exceeding their maximum germination temperature (41/190). Conversely, 95% of species at latitudes above 45° are predicted to benefit from warming, with environmental temperatures shifting closer to the species’ optimal germination temperatures.

Main conclusions

The prediction that tropical plant species would be most at risk under future climate warming was supported by our data, but through a different mechanism to that generally assumed.

Read more: https://onlinelibrary.wiley.com/doi/abs/10.1111/geb.13117

University of New South Wales is home to Ship of Fools Professor Chris Turney, leader of an expedition to the Antarctic to study melting ice which got stuck in the irony.

I love this new study because in my opinion it is a perfect example of climate scientists discarding or ignoring observations which do not fit their model.

There is no chance anthropogenic CO2 will lead to 1000ppm CO2, let alone 2000ppm, because there is nowhere near enough recoverable fossil fuel available to achieve early Eocene levels of atmospheric CO2. Since tropical plants handled early Eocene temperatures just fine, and we will never achieve early Eocene CO2 levels, there is no chance anthropogenic CO2 poses any kind of existential threat to tropical plants.

But the most extreme climate models predict lethal tropical temperatures by the end of the century.

A few climate scientists have courageously pointed out this contradiction means worst case climate model predictions about future tropical conditions must be wrong. But the rest just seem to blindly follow the output of their computers, and make alarmist statements which in my opinion bear no relationship to reality.

Note: If you ever see the bird in the picture at the top of this post in the Aussie tropics, don’t bother it, get as far away from it as you can. Like most Aussie wildlife Cassowaries want to kill you, and have a good chance of succeeding.

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July 4, 2020 at 09:02PM

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