Back in 1992, a group of scientists from around the world told us that we were ruining Earth.
Human actions like pollution, deforestation and ozone depletion were putting the planet on a dire course headed straight for destruction. We needed to change, or our planet would no longer be able to support life.
Ominously titled World Scientists' Warning to Humanity, the document said: "Human activities inflict harsh and often irreversible damage on the environment and on critical resources. If not checked, many of our current practices put at serious risk the future that we wish for human society and the plant and animal kingdoms, and may so alter the living world that it will be unable to sustain life in the manner that we know."
We didn't listen. And obviously not much has changed. Now, in short, we're pretty much fucked, and there needs to be a major change in order to save Earth.
Over 15,000 scientists from 184 different countries have now issued an even more catastrophic "warning to humanity", detailing the shocking decline in forests, wildlife and sea life on Earth and painting a pretty sad picture for the future of our planet. Scientists everywhere are raising the alarm, saying we're on course for a mass extinction event.
The second letter to humanity takes a look at the warnings issued 25 years ago and assesses our progress toward solving them. Unfortunately, we've done a terrible job. Despite the dangers, by and large the human race has done nothing while the planet has been pushed to its limits. Every single issue has gotten worse, scientists have pointed out, except the ozone layer.
Population is the major problem. In the past 25 years population has grown by 2.1 billion from 5.5 billion to 7.6 billion. Meanwhile, the population of every other animal has declined by almost 30%.
The new letter explains how our growing global population will soon be too much for our planet and eventually (much sooner than we realise), we will run out of natural resources.
It says: "Soon it will be too late to shift course away from our failing trajectory, and time is running out. We must recognise, in our day-to-day lives and in our governing institutions, that Earth with all its life is our only home."
And our future looks pretty bleak when you look at the data. In the last 25 years, nearly 300 million acres of forest have been cleared, and ocean dead zones, where pollution is so severe that virtually nothing can survive, have increased by 75 percent.
Scientists are now hoping that this second warning will make people take notice and help to change our collision course. Basically, we need to change before we destroy our planet entirely - or it destroys us.