16 January 2021 | New Scientist | 15HOME is your sanctuary, unless you
are a tree frog and a nice-looking
retreat contains a spider seeking
to make a meal of you.
Researchers in Madagascar found
a trap in which a huntsman spider
(Damastes sp.) was feasting on a
tree frog (Heterixalus andrakata).
“The spider had grabbed the frog
and was starting to suck out the
body of the frog,” says Dominic
Martin at the University of
Göttingen in Germany.
His colleague, Thio Fulgence at
the University of Antananarivo in
Madagascar, noticed that the spider
had been hiding between leaves
it had stitched together with its silk.
In the following weeks, he found
three other instances of leaves sewn
together, with huntsman spiders
waiting at the back (Ecology and
Evolution, doi.org/fqc7). The spiders
may build these traps specifically
to catch tree frogs, which hide from
predators in overlapping leaves. ❚Animal behaviourAIR pollution can worsen
the local effects of hurricanes,
according to a study of 2017’s
devastating Hurricane Harvey.
Harvey was “one of the
biggest hurricanes in the
history of the US”, says Renyi
Zhang at Texas A&M University.
It struck Texas and Louisiana
in August 2017 and caused
particularly severe flooding
in the city of Houston, Texas.
More than 100 people were
killed and the storm also gave
rise to major economic losses.
Even at the time, many
scientists argued that the
severity of Harvey’s impact was
a catastrophe partly of our own
making. For example, Houston’smany tall buildings may have
funnelled water vapour upwards,
making the rainfall and therefore
the flooding worse.
Zhang and his colleagues
now have evidence that another
human-linked factor was at
work: aerosol pollution from the
many petrochemical plants and
factories surrounding Houston.
For rain to fall, water vapour
in the air must condense to
form droplets of liquid water.
“To form droplets, you need
cloud condensation nuclei,” says
Zhang. These can be particles of
dust or sand, but they can also
be aerosol particles released
from burning fossil fuels.
The team found that theheaviest rainfall occurred in
the regions around Houston’s
petrochemical plants. Lightning
also clustered there: 230,
lightning strikes occurred over
three days in those regions when
the hurricane was stalled over
the coastlines of Texas and
Louisiana (Geophysical Research
Letters, doi. org/fqdj).
Zhang and his colleagues
used a computer model to
simulate Hurricane Harvey’s
effects in two scenarios: one
that included the aerosols frompetrochemical plants and
one without them. When the
aerosols were removed from
the simulation, both the flooding
and the lightning strikes were
reduced and no longer matched
the observations. The team
estimates that the aerosols
doubled both rainfall and
lightning in central Houston.
Zhang says the next time
a hurricane approaches, it
might be wise to shut down
petrochemical plants for the
duration. “It does seem like
if you keep injecting the aerosols
into the storm when there’s a
hurricane, you’re going to cause
more flooding and lightning.” ❚EnvironmentPollution made Hurricane Harvey worse
Joshua Rapp LearnSneaky spiders trap frogs
Huntsman spiders stitch leaves together to lure in tree frogs
DO
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AR
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“ If you keep injecting
aerosols into the storm,
you’re going to cause more
flooding and lightning” Michael Marshall