Freshwater systems are some of the most threatened ecosystems in the world. Factors contributing to their degradation can be associated with the expansion and intensification of agriculture in the 20th century, which has led to habitat degradation and water pollution. To mitigate the impacts of agricultural activities and improve stream ecosystem quality, government-funded conservation programs have promoted the implementation of best management practices (BMPs) during the last three to four decades. However, these conservation programs have been implemented within agricultural landscapes without evaluating exhaustively their potential side effects on freshwater species at the watershed scale. This study aimed to assess the changes in freshwater biodiversity in terms of fish species richness under future climate and potential conservation land-management schemes in the Kaskaskia River Watershed, Illinois, USA. Fish regression models were integrated to the Soil and Water Assessment Tool (SWAT) to simulate the responses of total- and game-fish species richness to four major management practices (crop rotation, cover cropping, reduced tillage, modified fertilizer application) identified as the most feasible in terms of stakeholder acceptability and environmental soundness, under 32 distinct climate projections. Results showed that fish species in the KRW are more sensitive to changes in the climate regime than to changes in the land-management practices. Specifically, the most likely percentage changes in fish species revealed a potential decline in richness in all stream orders over time with the worst impacts in the first and second order streams (-5%–-10% decade⁻¹) due to the progressive increase in the temperatures (0.61 °C –0.92 °C decade⁻¹) expected in the watershed. The long-term impacts on fish species richness may be inevitable if the proposed land-management alternatives were not accompanied by additional measures specifically design to protect aquatic life.

淡水系统是世界上最受威胁的生态系统。导致其退化的因素可能与20世纪农业的扩张和集约化有关，这导致了栖息地退化和水污染。为了减轻农业活动的影响并改善河流生态系统的质量，在过去三到四十年中，政府资助的保护计划促进了最佳管理实践（BMP）的实施。但是，这些保护计划已在农业景观中实施，而没有详尽评估它们在分水岭规模上对淡水物种的潜在副作用。这项研究的目的是根据美国伊利诺伊州卡斯卡斯基亚河流域未来气候和潜在保护土地管理计划下鱼类物种丰富度来评估淡水生物多样性的变化。将鱼类回归模型与土壤和水评估工具（SWAT）集成在一起，以模拟总鱼类和野味鱼类物种丰富度对四种主要管理措施（作物轮作，覆盖作物，减少耕种，改良肥料的施用）的响应。在32个不同的气候预测下，就利益相关者的可接受性和环境稳健性而言，最可行的方法。结果表明，韩国的鱼类对气候制度的变化比对土地管理做法的变化更敏感。具体来说，^-1）归因于流域中预期的温度逐渐升高（0.61°C –0.92°C十进制^-1）。如果拟议的土地管理替代方案未伴有专门设计的保护水生生物的措施，那么对鱼类物种丰富度的长期影响可能是不可避免的。