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https://www.theguardian.com/environment/article/2024/aug/05/all-night-streetlights-make-leaves-inedible-to-insects-study-finds>
"Streetlights left on all night cause leaves to become so tough that insects
cannot eat them, threatening the food chain, a study has found.
Scientists noticed that trees in urban ecosystems showed far less damage than
those in more rural areas. Their research, published in
Frontiers in Plant
Science, has shed light on a potential reason.
“We noticed that, compared with natural ecosystems, tree leaves in most urban
ecosystems generally show little sign of insect damage. We were curious as to
why,” said the study’s author, Dr Shuang Zhang of the Chinese Academy of
Sciences. “In two of the most common tree species in Beijing, artificial light
at night led to increased leaf toughness and decreased levels of leaf
herbivory.”
Artificial light from streetlights had a surprising effect on the leaves of
trees surveyed. The scientists tested two common species of street tree in
Beijing: Japanese pagoda and green ash trees. The pagoda trees have smaller,
softer leaves that insects prefer to munch on. Researchers thought plants in
areas with high levels of artificial light may focus on defence rather than
growth, which would mean their leaves would be tougher, with more chemical
defence compounds.
To test the trees they found 30 sampling sites on main roads that are usually
lit by streetlights all night. They measured the amount of light – illuminance
– at each site and then tested the leaves of the trees for toughness. They
tested almost 5,500 leaves for properties including size, toughness, water
content, and levels of nutrients and chemical defences.
If the leaves were larger, this would indicate that plants directed their
energy to growth of leaves, but if they were tough and contained tannins or
other chemical defences this would indicate that they had allocated their
energy to defend themselves.
They found that the more illuminance there was, the tougher the leaves. In the
areas lit the brightest at night, the leaves were extremely tough and showed no
sign of insects munching on them."
Cheers,
*** Xanni ***
--
mailto:xanni@xanadu.net Andrew Pam
http://xanadu.com.au/ Chief Scientist, Xanadu
https://glasswings.com.au/ Partner, Glass Wings
https://sericyb.com.au/ Manager, Serious Cybernetics
