In June 2001, the United Nations began a systematic assessment of the health of Earth's ecosystems. The assessment was completed in March of this year. Reports summarizing the findings of this Millenium Ecosystem Assessment are now available online.
There are a planet's worth of findings in the assessment's reports, and so there's no way for to even summarize them in one blog entry beyond this simple statement: We and the other living things of the Earth are in big trouble.
More about the Millenium Ecosystem Assessment:
The MA synthesizes information from the scientific literature and relevant peer-reviewed datasets and models. It incorporates knowledge held by the private sector, practitioners, local communities, and indigenous peoples. The MA did not aim to generate new primary knowledge, but instead sought to add value to existing information by collating, evaluating, summarizing, interpreting, and communicating it in a useful form.
For a quick overview check the GreenFacts.org Summary.