The "USDA Plant Hardiness Zone Map" is a strong indicator of CLIMATE.

The climate plants grow in is reflected in these maps. As the climate becomes warmer the hardiness zones migrate north from the warmer south. The protections of the forests will help push back against warming. Why?? Because trees are full of water and more importantly WATER PROCESSES THAT PRODUCE WATER VAPOR.

Walking into a forest under a canopy of leaves, the air is cooler and full of water vapor that makes it easier to breathe, too.

Every tree, shrub or herbaceous layer has a hardiness zone map, including those listed here for the discussion I have engaged all these months.

The 2012 USDA Plant Hardiness Zone Map (click here) is the standard by which gardeners and growers can determine which plants are most likely to thrive at a location. The map is based on the average annual minimum winter temperature, divided into 10-degree F zones.

For the first time, the map is available as an interactive GIS-based map, for which a broadband Internet connection is recommended, and as static images for those with slower Internet access. Users may also simply type in a ZIP Code and find the hardiness zone for that area.

No posters of the USDA Plant Hardiness Zone Map have been printed. But state, regional, and national images of the map can be downloaded and printed in a variety of sizes and resolutions....