The following article

Thousands of Venomous Portuguese Man O’ Wars Wash Ashore in Australia: ‘It Was the Stuff Of Nightmares’

details an event where a large number of a jellyfish creatures washed up on a beach in Australia. Mostly, the article is just about the alien and disturbing nature of the sight. However, the author claims:

It’s a sight we’re going to have to get used to in our warming world.

I understand jellyfish beaching is not all that rare, and seems mostly related to windstorms and tidal conditions conglomerating the creatures much in the same way weeds and garbage tend to wash up in bunches.

They give an explanation, which is that the jellyfish reproduce more in warmer waters, but I still remain skeptical there's been an increase, or that there will be an increase in the future.

  • 3
    Most experts will tell you that it's difficult if not impossible to ascribe a single incident (vs, say, ten successive nasty Atlantic tropical storms) to "global warming". If this recurs year after year, of course, the evidence will be more compelling. But of course if you wait another 10 years "just to be sure" then the chances off controlling anthropomorphic climate change will be very slim. Nov 2, 2017 at 23:45
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    @Daniel I'm asking specifically if the rate of this event type has increased in the first place. If yes, determining climate change as the cause is understandably difficult, but I doubt there's been a rate increase in the first place.
    – fredsbend
    Nov 3, 2017 at 1:06
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    I don't see anything in the linked article claiming that jellyfish wash up on the beach due to climate change. As I see it the article claims: 1) Washing up is normal and happens regularly. 2) Climate change increases the jellyfish population, thus the same percentage of jellyfish being washed up is a greater overall number. 3) Jellyfish [live and] wash up in specific locations, where water is warm, so with waters getting warmer globally, locations that didn't experience jellyfish frequently now do so (I recall same problem happening in UK).
    – Alice
    Nov 3, 2017 at 14:02
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    By the way: Man O'Wars are one of the less dangerous jellyfish you can encounter at Australian beaches. Check out sea wasps.
    – Philipp
    Nov 3, 2017 at 14:12

1 Answer 1


In several articles I've found about it, climate change is only but one factor among several other which have contributed to the boom of jellyfish population. The increase of the jellyfish population, however, has been acknowledged in several places of the world, and it seems to be a global trend.

Jellyfish are booming because of:

  1. Lack of predators due to overfishing.
  2. Overabundance of nutrients due to fertilizers being dumped into the sea as sewage waters.
  3. Warmer waters due to global warming.

Just point 3 is linked to climatic change, although it remains an important factor.

EDIT: I know this is old, but I've found some sources which paint a much better and more accurate response. The relationship between climate change and increasing population, or frequency of washup on the beaches, of jellyfish is currently under investigation:

In 2012, a task force of international jellyfish experts evaluated the scientific evidence behind the theory that jellyfish blooms were increasing as a result of global temperature changes. What they found, first and foremost, was a lack of information. Jellyfish are notoriously difficult to study, blooming unexpectedly in inaccessible corners of the sea. The data that were available suggested a more complicated story, in which jellyfish blooms occur in waves that coincide with natural fluctuations in the environment. While there was a slight upward trend of blooms in recent years, that increase was within the normal range of variability. The group didn’t reject the jellyfish-climate link, but they suggested that there might be other explanations for the increase in jellyfish abundance.(1)

If you are interested, the alternative explanations were mostly anthropogenic as well, mainly overfishing and destruction of maritime wildlife and biomes and contamination due to gray waters.

On the issue on why they end washing up the beaches, it's all in the currents and streams of the oceans, and there's a novel study which aims to predict the probability of jellyfish on spanish shores thanks to a metereological study of several athmospheric indexes (source in spanish).

  • 1
    This is a good start. Jellyfish populations have increased. But have there been more wash ups? +1 In advance.
    – fredsbend
    Nov 3, 2017 at 14:31
  • @fredsbend Old topic, but I've added some new references.
    – Rekesoft
    Jun 10, 2020 at 11:58

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