1. They are Slow Migrators

• If cloud forest species are unable to migrate fast enough to keep up with the rate at which climate change is shifting climatic optimums, then these systems will not survive. In general, the migration rates of montane species are estimated to be significantly slower than those of lowland species (7). One specific study on Amazonian cloud forests documented the historic changes in climate and forest composition over the last 48,000 years. By analyzing the region’s fossilized pollen record, Bush et al. (2004) estimated that climate change occurred at a steady, gradual rate over time, averaging less than 1 degree C every 1,000 years. Predictions for global warming project 1 to 4 degree C warming within the next 100 years (3). As Bush et al. point out; this projected change is ten times greater than even the most rapid temperature change in the past 48,000 years.

• Slow growth and maturation rates exacerbate migration difficulties. In addition to reaching a new site, forest species must also complete their life cycle before the climate envelope has passed (7). Studies predict that the establishment of a new, mature montane tree line takes at least 200 years (12). Furthermore, tropical moist cloud forests have the slowest recovery rates of all tropical forests, meaning that the damages inflicted to these systems from climate change will be particularly destructive (4).

2. They Have Narrow Ranges

• The environmental requirements necessary to support tropical cloud forests limit the ranges of these systems to hairline bands of altitude averaging approximately 500 meters (3). As climate change shifts the altitudes of ecotones, plants with particularly narrow ranges may be displaced from their climatic niche space within as little as one or two generations (3).

3. They are Poor Competitors

• The slow growth rates of many cloud forest species imply that they may be ill equipped to compete with new and nonnative species. Climate change is likely to increase competitive threats by (1) encouraging invasion from lower altitude species into cloud forest habitat, (2) increasing disturbance-induced canopy openings that allow for the establishment of fast-growing pioneer species, and (3) forcing cloud forest migration into new regions where they may not have the competitive advantage (7; 15).

4. There are Obstacles In the Way

• Environmental obstacles may also impede successful migration. Physical barriers might include rivers, roads, etc. The fact that many cloud forests are already situated at the top of mountain peaks, and thus would have no higher altitude to which they might migrate, poses another potential problem. Anthropogenic disturbance is also an issue. Deforestation and fragmentation reduce the likelihood that an undisturbed site will be available for migration