It's the average temperature at which trees start to die, not the average temperature over a year.
Just a couple of weeks at that temp will do a lot of damage.
The point is that ~2C or so from the pre-warming baseline you start seeing signs of a mass die off. And ~4C or so the damage starts to become systemic and irreversible.
45C average is insane! but thankfully a worst-case scenario - not the current situation.
Here is the present day temperature readings, from the abstract:
>>> Here we found that pantropical canopy temperatures independently triangulated from individual leaf thermocouples, pyrgeometers and remote sensing (ECOSTRESS) have midday peak temperatures of approximately 34 °C during dry periods, with a long high-temperature tail that can exceed 40 °C.
Considering that the models predicting the worst cases have tended to be more accurate (eg https://www.nature.com/articles/nature24672), you may want to hold off on that thankfulness.
leaf temperature is the issue. photosynthetic machinery begins to denature at 30C leaf temperature, this is physiologic break even point.
plants become stunted and just survive, rather than produce net gain of biomass
I live in a desert climate where it not only hits 46C, but does so for literally months on end. This article is utterly BS. Trees do fine, even an huge number of imported species from significantly cooler climates.
They survive, they're not 'doing fine', if they did you wouldn't live in a desert climate for long. High temperatures have a very visible effect on vegetation, so much so that you can trivially pick these out on satellite imagery.
Just a couple of weeks at that temp will do a lot of damage.
The point is that ~2C or so from the pre-warming baseline you start seeing signs of a mass die off. And ~4C or so the damage starts to become systemic and irreversible.