A Plague of People?

Alien Ecologists 

What would alien visitors studying Earth's ecology for the first time conclude? Let's stop thinking about ourselves as something special for a while and instead, think of ourselves as just another species of mammal. Where do we fit in Earth's ecological system?

Where did we fit?

Before we discovered how to make tools, we probably sat somewhere in the lower-mid part of the predator hierarchy. Technology changed that. 

Once we developed clubs, spears and arrows we moved up the predator ladder. Weapons and co-operative hunting techniques enabled us to kill animals much larger and more dangerous than our unarmed selves. It is no coincidence that, wherever we went, the giant mammals that once ruled the land died out. Technology continued to advance to the point where, today, we are the apex predator, all across the globe.

The Agriculture Problem

The beginnings of agriculture seems to be the domestication of pigs in Mesopotamia around 11,000BC. Prior to that, humans were hunter-gatherers and as such would have had relatively little impact on the landscape. They lived in and with their natural environment.

As agriculture extended to other crops and livestock, and the population grew, farming spread across the land. Today, 50% of the habitable land on the planet is occupied by it. That is 50% of the habitable land denied to the natural species that went before. 50% of the available land where the original plant and animal occupants are excluded and usually exterminated as pests.

The Population Problem

As I write this, the Earth's population is estimated at a little above 7.7 billion people and increasing. By the end of this century, the UN predicts it will be just under 11 billion. As compared to other mid-sized mammals, this is a huge number. For example, estimations for other common widely distributed species range in the low-mid tens of millions for dolphins up to about a billion and a half for domestic cattle (and they are only there because of us). As for one of our closer animal relations, the chimpanzee, there are only somewhere between 172,000 and 300,000 left.

The effects of us

In what is a geological instant, Earth has gone from being a place of abundance to one of all manner of threats to its many species of flora and fauna. To name a few, these include:

• Being hunted/harvested to extinction.
• Desertification
• Loss of habitat or food sources due to competition from humans.
• Pollution.
• Conversion of natural habitats for other purposes by humans.
• Deliberate poisoning by humans to prevent competition for food sources (i.e. crops).

And I haven't even mentioned the biggie; climate change, which is significantly contributed to by that one species; us. Sorry, but the ever-growing body of science on that subject is now pretty much conclusive.

The Alien Solution

Our alien visitors would see the great numbers of humans compared to the populations of other species. They would also see the vast areas of Earth damaged by agriculture. 

From their observations, our alien visitors would likely conclude Earth's ecosystem is way out of balance. I think they would go so far as to conclude that humans were present in plague proportions.
Given humans' propensity for driving other species to extinction, devouring Earth's resources as if there was an infinite supply (there isn't) and generating all sorts of harm to the planet's biosphere, our alien visitors could justifiably conclude we were a pest species.
Would our alien visitors then conclude that they would be doing Earth a service by exterminating us, so that the millions of other species of life on Earth could survive?

Looking at Earth from the perspective of all its life forms, what have we done to make it a better place?