Okay, looking back I realize my critique may be less than helpful without specific examples. So in case the author (and Thucy) is still interested...
The first thing I clicked on was "The Case for Our Survival." Based on the opening paragraph, I quickly skimmed the rest of the essay and a few others, and came to the conclusion that it was fairly representative. The paragraph in question reads:
"Although our survival is perpetually at stake as a species we do not often genuinely despair at the thought. The existence of our species lies outside of our control as we helplessly drift through a vast ocean aboard tiny life raft Earth. Yet there are even some people who question whether humans should survive. Consider the following..."
Read the original first sentence versus:
"Humanity's survival is perpetually at stake, but few despair at the thought."
This conveys the same meaning in a less cumbersome fashion.
"Humanity's survival is not guaranteed, and few even consider it."
Even cleaner, and to my mind, more accurate.
"Humanity's survival is far from guaranteed, and few even realize it."
A subtle bit of alliteration is usually good, and the "realize," while perhaps not as accurate, flows better.
Read them all aloud against the original. Which has the best rhythm? Which is the most clunky?
In place of the second sentence you should describe the myriad dangers humans face, for those who hadn't considered it. I wouldn't correct the wording so much as the imagery. Here, I would argue, is where you can purplefy your prose a bit - unleash the horrors of dinosaur-killing asteroids upon your reader, nuclear war, drug-resistant superbugs, whatever your favorite axe is to grind.
Remember: Who is your audience? If you're looking for mutual masturbation among like-minded individuals, I wish those of you in the circle-jerk all the best. But shouldn't you instead be trying to convince a misanthrope like me, who would cheerfully sacrifice a billion strangers for a guaranteed five extra years of healthful longevity for my dog and cat? You need to make me cheer for those plucky humans, surviving against all odds.
Once you've shown how fragile our hold on existence is, then you get to the main theme. The third sentence can be cleaned up a bit as well. Read the original versus:
"Yet there are those who question whether we should survive."
Or you could punch it up a bit and go with:
"There are those who say we shouldn't survive!"
To go any further I'd have to start charging for my services, but this is the stuff I'm talking about. Blow off some of the chaff and it will be a smoother read. Clean it up, find the rhythm.