Holdridge life zones

[3] The three major axes of the barycentric subdivisions are: Further indicators incorporated into the system are: Biotemperature is based on the growing season length and temperature.

Holdridge's system uses biotemperature first, rather than the temperate latitude bias of Merriam's life zones, and does not primarily consider elevation directly.

[8] Some research suggests that under the scenario of continually increasing greenhouse gas emissions, known as SSP5-8.5, the areas responsible for over half of the current crop and livestock output would experience very rapid shift in its Holdridge Life Zones.

This includes most of South Asia and the Middle East, as well as parts of sub-Saharan Africa and Central America: unlike the more developed areas facing the same shift, it is suggested they would struggle to adapt due to limited social resilience, and so crop and livestock in those places would leave what the authors have defined as a "safe climatic space".

In contrast, under the low-emissions SSP1-2.6 (a scenario compatible with the less ambitious Paris Agreement goals, 5% and 8% of crop and livestock production would leave that safe climatic space.

Holdridge life zone classification scheme. Although conceived as three-dimensional by its originator, it is usually shown as a two-dimensional array of hexagons in a triangular frame.
On this map, a shift of 1 indicates that at the end of the century, the region had fully moved into a completely different Holdridge zone type from where it had been historically. The extent of the shifts will be dependent on the severity of the climate change scenario followed. [ 8 ]
Areas of the globe where agriculture would become more difficult perhaps to the point of leaving the conditions historically suitable for it, under low-emission and high-emission scenarios, by 2100. [ 8 ]