Don't ants and termites have technoculture?
I'm torn on that, but either way they don't have ratcheting technoculture, which is what makes us different from all other species. The Ratchet has not been demonstrated in any species (other than one study suggesting that New Caledonian crows have ratcheting culture). But even in that case their ratcheting culture would be very primitive (i.e., not very complex - 3-4 "steps").
Does our being "the/a global brain" imply that we destroy our lifebase and deplete our renewable and nonrenewable ressources?
No, quite the opposite. If we become a true global brain it will likely be a civilization based on solar (IMO).
Doesn't our failure to address our most basic problems, like overusage, pollution, urban sprawl and agricultural soil loss, testify to our "brainlessness" and lack of insightful coordination, in spite of our new "global nervous system", the internet?
These are major problems that stem from the development of the industrial revolution. They are major concerns and will be critical to overcome in the 21st century. The technologies to accomplish this either A) already exist, or B) are in our not-to-distant future.
The Internet will play a key mediating/communication role in allowing us to dynamically solve problems on a global scale. Remember the Internet is new and still evolving rapidly. We will become far better coordinating and cooperating globally in the 21st century (when compared to any other century, including the 20th).
It appears to me that your analogies are spectacularly anthropocentric
You would have to give me specific examples and tell me why they are anthropocentric. Most people would say the opposite, considering I believe humanity is the process of becoming a different higher intelligence (post-humans/transhumans).
Richard Heinberg compares our collective global intelligence with that of a population of bacteria in a petri dish, its population collapsing after its food/energy base is depleted.
His comparison would make sense if we controlled for memes. Global humanity and bacteria share the same system pattern; however they differ in their primary information transfer mechanism. The reproduction and complexification of our "memesphere" or "memnome" will allow is to stabilize a global civilization because they are more flexible and can evolve to solve problems without replacing the agents themselves (i.e., humans or post-humans).
Our food/energy bases now are soil and oil, and we are rapidly depleting both of them, incurring increasing environmental dammages.
We are obviously in the process of transferring to renewable energy sources. Our success as a global civilization depends on this happening - I believe we will successfully do this - if you disagree that's fine - but you are part of the problem if you aren't helping solve it.