Discussion
The cloudiness of TMCF is vital to the functioning of these ecosystems.
It has been predicted that the cloudiness of these ecosystems will
likely decline (Helmer et al., 2019), but until now, recent trends have
not been formally quantified. Using state-of-the-art climatic databases,
our study assessed trends of low CF in these ecosystems, revealing that
most of the evaluated TMCF already present low-cloud reductions. We
further unpack the association of the observed trends with other ECVs
globally and regionally at the biographical realm level. The following
sections highlight the key aspects of our findings and offer broad
insights into future TMCF.
4.1 Trends of low-cloud fraction
Our results based on ERA5 reanalysis indicate that TMCFs face reductions
in low-clouds at higher rates than tropical landmasses. Our estimates
and their uncertainties at the biogeographic realm level also reveal
that the decline in low-clouds might be associated with regional
drivers; thus, it cannot be concluded that all TMCFs are experiencing
cloudiness decreases. In this sense, Neotropical TMCFs are among the
sites with the highest reductions in low-clouds. Neotropical TMCFs are
also likely to be the most affected, given their substantial increases
in surface temperature, dew point, pressure, and PET, and their
significant reductions in precipitation and VSWC. Predictions by Helmer
et al. (2019) suggest that 57% to 86% of the existing Neotropical TMCF
zone area will experience decreases in cloud immersion. Similarly, our
results indicate that 79.1% of the evaluated Neotropical TMCFs already
showed reductions in low-clouds. Furthermore, our perception that
regional factors may be responsible for cloudiness declines in some TMCF
is supported by Los et al. (2021), who observed an increase in cloud
base height in America’s TMCFs over the past four decades, but a
decrease in Asia’s TMCFs. Helmer et al. (2019) predictions, Los et al.
(2021) findings, and our results support the idea that Neotropical TMCFs
are under threat, and thus species and essential ecosystem services that
these ecosystems provide (Mayer et al., 2022; Mulligan, 2021).