Long-running measurements from two Caribbean forests point to a shared rise in hot days, but different changes in rainfall. A peer-reviewed study of La Selva in Costa Rica and El Verde in Puerto Rico found that both sites warmed, while heavy rain increased at one and dry days increased at the other. The results show how regional climate change can take distinct forms from one forest to another. [S1]
The researchers analyzed records of air temperature, precipitation and stream conditions. The air-temperature records covered 1992–2024 at La Selva and 2000–2024 at El Verde. Precipitation records began earlier: 1983 at La Selva and 1975 at El Verde. These long time series let the team compare changes in average conditions with shifts in unusually hot, wet or dry days. [S1]
Average air temperature rose by an estimated 0.29°C per decade at both sites. The change in extreme heat was more pronounced: using each site’s own 95th-percentile temperature threshold, the modeled number of hot days rose from about eight per year at the start of the records to about 35 in 2024. The researchers say much of this increase was driven by high temperatures in 2023 and 2024, so the latest years strongly influence the pattern. [S1]
Rainfall tells a less uniform story. At La Selva, days with no rain declined from 128 in 1983 to 70 in 2024, while the frequency of the heaviest rainfall events increased. Rainfall above the site’s 99th-percentile threshold rose from about one event per year in 1983–1985 to six in 2024. At El Verde, the number of dry days—defined in this analysis as days with less than 1.4 millimeters of rain—increased from 152 to 170 per year. The study found no significant increase in heavy-rain events there. It also found no significant long-term change in daily precipitation at either site. [S1]
The distinction matters because a long-term average can conceal shifts in the timing and intensity of rain. Fewer rainless days at one location can occur alongside more heavy downpours, while another location can experience more dry days without a measured rise in heavy rain. Such differences may matter for forest and stream ecosystems, but this study tracked climate and water conditions rather than directly measuring ecological effects. [S1]
Stream temperatures also increased over the periods studied: by 0.2°C at La Selva and 0.9°C at El Verde. The researchers observed a tendency for high water levels to last longer at both sites, with estimated durations roughly doubling. However, the statistical evidence for those water-level trends was marginal (p = 0.08 at each site’s reported threshold), so the findings do not establish a clear trend in high-water conditions. [S1]
The results describe two monitored locations, not the whole Caribbean. The authors also report that the estimated air-warming trend is sensitive to the informative prior used in their model, which was based on regional warming information. And because the rise in hot days was largely driven by 2023–2024, future observations will help show how persistent that pattern is. The study documents local climate shifts; whether and how those shifts are changing forest productivity, biodiversity or stream communities remains an open question. [S1]