Tropical biomass, fossil leaves and snow-eating nights open separate windows
Orbital lasers showed the three great tropical forests answering heat and drought differently; Wyoming leaf cuticles record canopy thinning 56 million years ago, while warm nights drain western US snowpack faster.
Science··Night
Three tropical forests answer the same climate stress differently
Phys.org reports that a team working with NASA-GEDI laser measurements compared 16 million forest biomass estimates from 2020 across the Amazon, the Congo Basin and Southeast Asia. GEDI fires laser pulses from orbit and reads the three-dimensional canopy structure, so biomass can be estimated without a field plot. Congo Basin forests were the most sensitive to temperature, Amazonian forests moderately so, and Southeast Asia forests barely at all. Water scarcity ran the other way: biomass in Southeast Asia fell sharply as conditions dried, the Amazon peaked at intermediate dryness, and African forests moved little. Soil, terrain and damage from storms, lightning and windthrow shifted the pattern further. Researchers at the Smithsonian Tropical Research Institute, the University of Maryland, NASA and a Brazilian partner published the work in Nature. It rests on a single year of observations, so it describes how standing biomass varies with climate across space rather than how any one forest will change over time. The map is a present-day spatial slice, not a future projection or a deep-time archive.[1]
Wyoming leaf traces write thinning from 56 million years ago
A separate Phys.org report says fossil leaf skin from the Wyoming Hanna Basin reconstructs the canopy of 56 million years ago and shows forests opening up and losing their largest trees. The Paleocene-Eocene Thermal Maximum is the closest natural analogue geologists have to a rapid carbon release, combining elevated atmospheric carbon dioxide with warming and reduced rainfall. Regan Dunn of the Natural History Museum of Los Angeles County and colleagues measured microscopic epidermal cells preserved in organic-rich rock and estimated leaf area index, how much leaf surface stands above a patch of ground. That index falls through the event. Dunn sets the pattern beside the present, where carbon dioxide has been fertilising plants and greening much of the land while heat and drought push other regions towards browning. The work was published in Science. Human emissions are adding carbon about an order of magnitude faster than the ancient release, so the ancient forests had far longer to adjust. This archive belongs to a deep-time slice in Wyoming; it does not share place or pace with the 2020 tropical laser map, and the two datasets cannot be fused into one forest story.[2]
Warm nights eat western US snow at nearly double the average rate
A third Phys.org report names several days and nights of above-freezing air over mountain snow between March and July the snow-eater heat wave. On those spells observed snow loss ran at nearly double the seasonal average. The team tracked the pattern through western US mountain weather from 1850 to 2015, using atmospheric reconstructions for the nineteenth century, when high-altitude stations were absent, and checking the result against modern snow-monitoring sites. Such spells arrive three to five times in a melt season and last three to five days each; what distinguishes them is the missing night-time refreeze that normally halts melt until the following afternoon. Seven of the eleven major snowmelt-driven spring superfloods in the western United States since 1950 began within five days of one. The work was published in Science Advances. The nineteenth-century half of the series comes from a model reconstruction rather than direct measurement, which matters most for long-term trend claims. On the night desk the tropical laser slice, the Wyoming deep-time archive and the western US snow window sit side by side; each must be read in its own place and time, and locations and eras are not fused.[3], [1], [2]
