Editing Environmental gradient (section)

===Altitude===
Altitude gradients are a key consideration in understanding migration patterns due to the effects of global warming. As temperatures increase, trees adapted to warmer climates will migrate uphill for access to sunlight, and thus populations of temperate or cold-adapted trees and the habitats suitable for them will shrink.<ref>{{Cite journal|last1=Ruiz-Labourdette|first1=Diego|last2=Nogués-Bravo|first2=David|last3=Ollero|first3=Helios Sáinz|last4=Schmitz|first4=María F.|last5=Pineda|first5=Francisco D.|date=2012|title=Forest composition in Mediterranean mountains is projected to shift along the entire elevational gradient under climate change: Forest dynamics under climate change|url=https://onlinelibrary.wiley.com/doi/10.1111/j.1365-2699.2011.02592.x|journal=Journal of Biogeography|language=en|volume=39|issue=1|pages=162–176|doi=10.1111/j.1365-2699.2011.02592.x|s2cid=82037043 |url-access=subscription}}</ref>