Macrobenthic animals living in a tidalflat area in the westernmost part of the Wadden Seawere monitored for 50 yr (1970−2019) using consistentmethods. About 100 papers were published on thisproject. We review a number of results and conclusions on observed changes and their possible underlying causal processes. The most significant changesin population sizes and growth rates of several speciescould be attributed to climate warming (by about2°C), along with increasing trends in species richnessand total late-winter zoobenthic biomass. In the initialyears, eutrophication (doubling of nutrients andchlorophyll concentrations) resulted in a doubling ofzoobenthic biomass. The subsequent de-eutrophication after the mid-1980s was reflected only in the biomass values observed in late summer. A long-termtrend in food supply for birds was not observed. Disturbances from fisheries were intermittent and modest. In several bivalve species, magnitudes of production and biomass were determined primarily byrecruitment variation, which was mainly caused byspring abundance of epibenthic predators (shorecrabs and shrimps). Their abundance in creased withtemperatures in the preceding winter. In contrast tothis top-down regulation, bottom-up processes apparently played only a minor role in the determination ofbivalve biomass. Rarely occurring extremely high bivalve numbers resulted in reduced rates of growthand production. We conclude that the uniquely longmonitoring of the tidal-flat macrozoobenthos yieldeddata series which not only indicated several longterm trends, but also contributed to our insight in processes underlying the observed trends. Most of theobserved trends were related to climate change andeutrophication followed by de-eutrophication.