I don't know if it is today or if I missed it but there was supposed to be a day where as many people as possible said something about the environment in their blog. Now I don't know how friendly turning a planet into a black hole is exactly. First of all there is very likely no ecology on Jupiter at all though if there is one all plans to destroy the planet become rather ahem a-moral. It is unlikely though that Jupiter has any life at all on it at least it has no earth like life. However one of it's 63 moons just might have something crawling or swimming around on it. Europa has liquid oceans on it and I believe there is a very good chance that it currently supports some kind of primitive life. If Europa did in fact have life in it's oceans then turning Jupiter into a black hole would be a black act indeed. Let me take a moment though and say that turning Jupiter into a black hole wouldn't have any dire consequences for Europa necessarily since it would be perfectly capable of sustaining its orbit around a Jovian massed black hole in exactly the way it currently maintains its orbit around Jupiter. However since Jupiter cannot be transformed entirely into a black hole all at once but rather a black hole would first form somewhere near it's center and then suck the rest of the gas giant into it. This process would give off a great deal of radiation and great streams of high energy particles. I really don't know whether this would be enough to cause any theoretical life under the ice of Europa any trouble but it would very likely be enough to at least melt the ice and would no doubt cause something of an ecological uproar if Europa did in fact have something that could fairly be called an ecology.
I would here like to say that I am not in favor of destroying Jupiter, I am in favor of creating a black hole. My desires for a local black hole outweigh the desire I have to preserve Jupiter. Should there be life that would be destroyed by this procedure of creating a black hole then I would say that the costs would now outweigh the gains. If the process of creating a black hole out of Jupiter's mass was such a violent process as to cause harm to the earth then I would say again that such a method was not advisable.
Lastly I would like to say that I find it very likely that the destruction of Jupiter is an action that will never find itself under serious consideration by an entity with the power to carry it out. Of course I also think that there is a distinctly non-zero chance that in the future humanity will discover some means of faster than light travel which will require the use of a region of highly curved time space such as that found inside a black hole. Now the question arises that if the destruction of Jupiter would allow us a gateway into the rest of the cosmos then would its destruction be worth the costs? The answer is very probably no. The solar system is a large enough place to play host to a great civilization. In the aeon's that it would take to fully utilize the resources of our humble home I think humanity could live a life much more grand than its due. However that does not mean I do not favor a more grand scheme in which humanity spreads through the stars. We must be wary of growth that comes with such destructive costs. If humanity sweeps through the galaxy destroying worlds in order that it can continue to sweep through the galaxy then perhaps we should consider that growth should not always be sustained but one must learn to live with balance.
All that is just to say that I don't see the creation of a black hole by the destruction of Jupiter as necessarily a good thing. What I do see is a fascinating possibility and a great technical challenge. This blog is not so much devoted to the idea that blowing up Jupiter is good as it is to the question of how might it be done or is it even possible?