This paper presents a method to conduct a systematic literature review (SLR) and meta-analysis studies on environmental science. SLR is a process that allowed to collect relevant evidence on the given topic that fits the pre-specified eligibility criteria and to have an answer for the formulated research questions. Meta-analysis needs the use of statistical methods that can be descriptive and/ or inferential to summarizing data from several studies on the specific topic of interest. The techniques help to generate knowledge from multiple studies both in qualitative and quantitative ways. The usual method has four basic steps: search (define searching string and types of databases), appraisal (pre-defined literature inclusion and exclusion, and quality assessment criteria), synthesis (extracts and categorized the data), and analysis (narrates the result and finally reaches into conclusion) (SALSA). However, this work added two steps which are research protocol (define the research scope) and reporting results (stating the procedure followed and communicating the result to the public) at the initial and last step, respectively.