biostudies-literatureDaugaard USwiss National Science FoundationUniversität ZürichUniversity of Zurich1974-1985https://www.ebi.ac.uk/biostudies/studies/S-EPMC9540476biostudies-literatureUnknown25(9)The potential for forecasting the dynamics of ecological systems is currently unclear, with contrasting opinions regarding its feasibility due to ecological complexity. To investigate forecast skill within and across systems, we monitored a microbial system exposed to either constant or fluctuating temperatures in a 5-month-long laboratory experiment. We tested how forecasting of species abundances depends on the number and strength of interactions and on model size (number of predictors). We also tested how greater system complexity (i.e. the fluctuating temperatures) impacted these relations. We found that the more interactions a species had, the weaker these interactions were and the better its abundance was predicted. Forecast skill increased with model size. Greater system complexity Ecology lettersForecasting in the face of ecological complexity: Number and strength of species interactions determine forecast skill in ecological communities.PMC9540476310030310030_188431188431Petchey OLDaugaard UMunch SBInauen DPennekamp FfalseForecasting in the face of ecological complexity: Number and strength of species interactions determine forecast skill in ecological communities.The potential for forecasting the dynamics of ecological systems is currently unclear, with contrasting opinions regarding its feasibility due to ecological complexity. To investigate forecast skill within and across systems, we monitored a microbial system exposed to either constant or fluctuating temperatures in a 5-month-long laboratory experiment. We tested how forecasting of species abundances depends on the number and strength of interactions and on model size (number of predictors). We also tested how greater system complexity (i.e. the fluctuating temperatures) impacted these relations. We found that the more interactions a species had, the weaker these interactions were and the better its abundance was predicted. Forecast skill increased with model size. Greater system complexity 2022-01-01T00:00:00Z2022 Sep2025-04-22T12:06:42.792Z2025-04-06T00:15:02.736ZS-EPMC95404763583126910.1111/ele.14070