Image: s_260x260 201412__Coconut_crab_in_Hawaii_&_A photo posted by Enrique Steven Victor (at)xsubsoniqx on Dec 12 2014 at 944pm
Just another interesting (only to me perhaps) info about these magic giants:
HuffingtonPost: Coconut crabs considered to be invasive in Hawai
More reasons to ensure that exotic species that may represent a danger to native species, including humans, should be kept either out or under cntrol.
What surprised me most in the above news was the fact that they treat Coconut crabs invasive in Hawaii. My understanding – based on previous info from Mike and Krishnan – was that these crabs are (were) common in the whole Indo-Pacific region originally mirroring the distribution of coconut palms. To me it seems that this species had became extinct in Hawaii and now they consider it invasive. From scientific viewpoint however this approach seems to be incorrect, not to mention that I can’t imagine what kind of danger could the Coconut crabs pose to other species given their slow growth rate and late sexual maturity. Otherwise, I totally agree that invasive species must be kept either out or under control, including plants, animals and humans. Cheers, Janos
Maybe they are over-reacting there Janos. Or has the crab mutated into some science fiction giants?
Yes, curious! They are very good to eat, so have gone from most of their range. I can understand the viewpoint above: that if they became extinct then the new ones might be called invasives. But here’s a question: does invasive necessarily mean bad?
The concept of Invasive Alien Species is very complex. No species is alien to the earth. It is only the range extension – to an inherently impossible place of normal occurrence on to willful planting for a vested interest. Only when a species gets established in an ecosystem to the detriment of the “sons of the soil”, we start worrying. Akin to the influx of people into UK from other continents and establishing an unquestionable Authority over the British in their own home towns. Such influxes have short or long term impacts, bizarre results, unexpected turn of events and some times total destruction of the whole system in a short span of time. In the past, we have seen the impacts of the Giant African Snail, Tilapia, the African catfish etc. Periplanata americana does enjoys distribution all over the world!!. In some cases, the gene pool also gets pounded. Who can draw the line of safety and on what principle is still a puzzle. As far as the coatal fish evolution is concerned Malayan Archipelago is the cradle, but now the cradle is infested with foreign elements. An african baby in the Philippine cradle is odd. A japanese daughter-in-law in an orthodox Norwegian family is no more a wonder!!. An American Priest of German origin in a Hindu temple is accepted by the society with pride. On one hand, the alien species, if invasive, has to be dealt with caution and on the other hand, if it enhance the complexion we have to welcome. Have a cake and eat it too.
Thank you Krishnan 🙂
So following the pathway of a Coconut crab in Hawaii we found at least three questions:
– Does invasive necessarily means bad?
– Is it appropriate to consider a species, re-introducing into a geographical area, from where it had became extinct, as invasive?
– Are there any evidences or known facts showing that coconut crab populations can pose harm in any way to populations of other species?
Further – probably interesting – questions would be: how many definitions can we find for the term ‘invasive species’ and which of those do we consider the most appropriate (general, complete)? One candidate can be the description of this term on Britannica.
Nice summing up Janos 🙂
Your questions raise some much wider issues. The first is the one that Krishnan mentioned : increasing or changing range of a species. We had a very long thread on Linked-in some time ago, in which most of the folk working with ‘invasives’ or responsible for national (indigenous) fauna & flora were very much against any new species arriving. I can understand this viewpoint. [Major conservation bodies throw 40% of their budgets at invasives].
My own view (& Krishnan opened with it) is that all species on Earth are part of our biosphere; they do belong here. Taking a holistic view I see that habitats shift over time, distribution of species alter, depending on physical conditions, such as rainfall or temperature. In times past we would have called this adaptation or evolution. Species would have been praised for adapting to new niches and habitats; outdoing species that were in decline. I think one of our issues is that humans think we are ‘smart’, but much evidence suggests otherwise. In cyber-times we certainly have the ability to gather information ~ but then we find ourselves unable to do anything with it, because much of our world governance, operating procedures, and society prevents us from success.
So one of the issues is ‘countries’. We assume lines on a map represent some other place, and each is sovereign unto itself. Yet, going back to the dawn of time, countries did not exist. We made them. Species were wherever they were; habitats are, still, dynamic ~ changing as conditions alter. Continental drift and plate tectonics. Humans emerged in East Africa some 7 million years ago and slowly ‘invaded’ the rest of the world.
I’m not against folk being concerned about invasive species, but I’ve always had the ability to see the bigger picture ~ a vital skil in marine research, because our habitat changes every day. We don’t see the same drops of seawater on 2 consecutive days ~ what was here yesterday is now elsewhere; land comes and goes, islands come up and erode. Species go wherever the food is, or comfortable temperatures or salinity exist. Migration is pretty normal. Different habitats make up a life cycle
Another major factor is human activity, as most texts suggest: a large numer of invasives are caused by our behaviour. We chop down a forest and the resident species have to go elsewhere ~ they are now invaders. They want to eat and reproduce, and have to adapt (evolve) to their new circumstances. If that means they are better at this than the previous incumbents, so be it: the old inhabitants now gain the privilege of the Red List. The incomers ~ successful species ~ are now pests, parasites, unwanted etc.
As with much else we’ve discussed at BA: we see the hand of humans everywhere, yet we are unwilling to accept cause-&-effect (Karma). Thinking aside for a moment, I realised last night why the USA is so unwilling to do anything proactive to reduce greenhouse gas emissions: their entire society is based on producing greenhouse gases: war, armed police, excessive use of vehicles, wasting electricity, commuting etc. They can’t change without stopping everything, and then only restarting things in a balanced, sustainable, eco-friendly way. So it’ll not happen.
I think the key is whether invasives are harmful or not? And what do we mean by harmful? Species succession and decline. I’m mindful that we seem to want to keep Earth locked into some pattern that we determine to be correct. But our world constantly changes, and we are now increasing that rate of change. Human population nigh on quadrupled in a century! On one hand we praise the ability of species to cross vast oceans and establish themselves on remote islands (biogeography; Darwin’s & Wallace’s theories on evolution); on the other we criticise them for doing so ~ by becoming invasives?