Biomeridians, or biological meridians, are a proposed standard for measuring the effects of global climate change on natural environments.

The first step in measuring long term change is getting a clear picture of nature as it is right now. Global time is measured relative to the prime meridian, the line of 0° longitude that passes through the Greenwich Royal Observatory. Similarly, a biomeridian defines a baseline for natural biodiversity, from which we can begin to measure change over time.