This paper introduces our project Causes and Effects, which visualizes California sea lion unusual mortality events (UME) to create a new layer of understanding of the situation as an important environmental issue. It examines the causes of and impacts on sea lion UME by controlling multivariate factors that impact sea lions’ health and stranding. Previous visualizations for sea lion mortality only captured temporal data and the relationship between causes and effects using simple graphs. However, sea lion UME results from multiple causes and it requires multivariate visualization to establish clear solutions for future results. The resulting images of our visualization allow users to explore how environmental factors impact the lives and situations of sea lions.