How well could all life on Earth, working together, defend the planet?

We would get wiped out like nations with better weapons and technology can whip the shit out of less advanced nations.

Well, if these hypothetical aliens saw guns, nuclear weapons, biological weapons etc. as like vows and arrows, I doubt the other animals of Earth would matter much to them.

I never saw Avatar, never will. However, I know that the enemy of my enemy is my friend, so I’d presume “all life of Earth” will defend just fine. I won’t automatically assume the the invaders have better weapontry or technology, and seeing that they’d come from like a billion light years away, they’d be awfully old even for Spacemen, so it really can’t be that hard regardless.

…what would they do if, say, billions of bugs attack them?

Assuming nothing on this planet act as a biological weapon against them? I don’t know, we’d probably die. But we would have home field advantage, and bows and arrows are still lethal. Working together with all of the flora and fauna too? I think we’d have a fighting chance.

I think our best chance at survival is to unload biological weapons on them, germ warfare the aliens, maybe our smallest life forms would be able to kill them.

We’d most likely die from intergalactic small pox. Don’t accept any blankets from space aliens just to be safe. Of course if that didn’t happen they would just corral us into work camps mining whatever it is that want and melting down whatever we had made. It would be not unlike the Spanish did to the Aztecs and their gold. IMO.

If things turn out like they do in Derrick Jensen and Stephanie McMillan’s graphic novel “As the World Burns: 50 Simple Ways to Stay in Denial”, then we’ve got a pretty good chance. Of course, one of the points of that is that we’d rally if it was space invaders, but sit at home and watch TV if it’s “our” governments and corporations doing it.

And of course, some of us ARE fighting.

Assuming they managed to develop some form of hyperspace leap device, they would most likely have technology we could not imagine. Let’s do a thought experiment anyway. How did they get here? In the form of a gas? Not likely. A liquid? Nope, too hard to control. A solid? Most likely a ship with an exoskeleton and support structure. What can we do to destroy something we don’t know anything about? Of all the elements and compounds in our limited known universe, given enough heat we can change its state: solid to liquid, solid to gas. So, if we can apply enough heat to a spot on the solid ship we can change its state disrupting its function. Where can we get a source of heat sufficient to change the state of a super solid? A fusion reaction- the temperature of the sun. A Hydrogen bomb.
They no doubt have shields, so we’ll need to penetrate those first. It would be wasteful to have a shield on full power at all times so it probably has some form of adaptive learning. Our goal is to get inside the shield passively then detonate.
Welcome them to our planet and treat them with respect as we would any emissary from an advanced civilization. Put a radio controlled H bomb in a wooden horse and offer it as a gift to our new supreme leaders.

There’s a counter-trope for this, called Humans Are Warriors.

Read Poul Anderson’s short story, The High Crusade sometime. Aliens, armed with better-than-modern weapons, FTL travel, gravity control, and all of the requisite science to back that up, land an enormous ship in a medieval English village – a village that had preparing to send troops out to join King Richard in France.
The aliens rely heavily on shock-and-awe tactics, are effective only with ranged weapons, and wear no armor – practically the opposite of the humans. The aliens are pwnt as soon as the would-be crusaders realize that these funny blue men are, in fact, mortal. They end up clearing out the ship.
The local baron decides to use his new toy to bring the entire village along with him to France, but alas! the lot of them are sent back to the ship’s base, and the records of Earth destroyed.
The rest of the story is about the baron’s conquest of the galaxy via superior battle tactics and advanced statecraft – skills that the blue aliens had lost after centuries of largely undisputed rule.

Um, even we couldn’t defend ourselves if we wanted to. The Earth’s entire arsenal of WMD’s is enough to wipe out all intelligent life on this planet.

The only thing our planet needs defending against, is us : (

I guess that what I was saying is that it depends on the kinds of aliens that we’re talking about. How advanced they are, and in which ways. Harry Turtledove has a story where the secret to gravity control – and thus, interstellar flight – is stupidly simple. The guys who discovered it never had a reason to develop very far past Earthside 17th century technology. They show up on a modern Earth and are annihilated, because muskets are the apex of their military development.

Animals would be wholly ineffective, unless the aliens started putting actual squishy bodies on the ground, out in the open.

If there were aliens who could cross interstellar space, we’d be totally screwed.

@windex

True story.

Even assuming the successful destruction/obstruction of alien ground forces by terran defenders, the moment the aliens realise that ground warfare is fruitless, they hopefully will commence orbital bombardement.
It is what should have been done in Avatar.

@ragingloli “Nuke the site from orbit – it’s the only way to be sure.”
Though that probably would have been prohibitively expensive – as it was, they had to manufacture their gear on-site. Maybe a biological agent?

lol…The way we treat animals….there is no way they would help us…they would just run away/hide…along with a lot of humans…. This was a stupid movie but take “Skyline” the aliens came…started attacking, and most people just hid wile the (ineffective) military tried to stop them…And even wile hiding for self preservation people in the groups still fought each other…As a species we are unable to “join together” to defeat a common foe…

We would be SOL

@coffeenut The trouble with movies – fiction in general, really – is that they don’t usually represent what would actually happen; instead, outcomes are governed by the whimsy of the writers. We don’t really know how we’d behave in the face of alien invasions, because we’ve never been invaded by aliens.
I think that the principle of “enemy mine” (no matter what the Seven Habits of Highly Effective Pirates says) would be sufficient to unite us against such an invasion; we see it throughout history, in the form of alliances (Joseph Stalin was only one of the Big Three because he’d been backstabbed by Hitler), politics (“Lesser of two evils/better the devil you know”), heck, even unions.
The aftermath of a successful alien invasion would be a different story entirely.

@Nullo Well I used a movie reference because the question is based on a movie….Avatar…

In general, country policies about warfare/invasion are pretty much the same….Civilians will evacuate/be evacuated from the danger area so military forces can mobilize and deal with the threat….That creates a high probability of us being “defenseless” if they fall… Then there is the fight/flight consideration where most of the (world) civilian population are not capable (training/mentally/physically) of fighting….(I can’t fly a fighter jet) And actually seeing a alien….that is trying to kill you…. Lastly our combined “might”.....our main weapons are only located in a few countries….and if they are ineffective or destroyed before we could destroy them we would be done. (Unlike a movie….we would just win in the end by the skin of our teeth)

Lol, and “Nature” wouldn’t mobilize to assist us…

Thanks for the answers @all—I don’t think I phrased my question exactly like I intended, but—the responses you all gave were interesting.

(I don’t expect answers again, I just want to try to phrase the question better: I was kind of wondering how strong all of the natural defenses life here has built up through time and evolution really are.
And if they were purposefully used with each other rather than by the creatures to survive against each other, how strong or not strong those defenses would be.) Hmm I don’t think I phrased it well again..

good idea