Systematic Review of the Factors Affecting Environmental Crimes

Environmental crimes are one of the important topics of green criminology. Green criminology deals with crimes and damages that affect the environment, plants, and lives of domestic and wild animals. The results of various reports indicate that the 5 areas of illegal trade in wildlife, timber and forest trees, substances that destroy the ozone layer, discharge of hazardous waste, and illegal fishing outside of the prescribed time are among the most important and common types of environmental crimes in the world. Crimes against the environment are one of the major cases of environmental destruction that have now become important national and global issues. During the recent decades, many studies have been conducted to identify and explain environmental crimes though they have sometimes had conflicting and contradictory results, which create ambiguities in this issue. Due to the abundance and diversity of research conducted in the field of environmental crimes, a combination of research in this area, like a systematic review, is felt to be necessary. The main question of this research was as follows: What are the most important factors affecting environmental crimes?

The research method of this paper was based on a systematic review and meta-analysis. The method of systematic review presents a summary of research results in the form of a table and uses the technique of counting opinions. It is a kind of summary of the existing literature and writings about a specific scientific topic, which uses certain methods to search the literature and critically evaluate each research. In addition to the systematic review, the meta-analysis method was used in this study. The term ‘meta-analysis’ means analysis of analyses. A particular topic may have been replicated in various ways by using, for example, differently sized samples and conducting research in different countries under varied environmental, social, and economic conditions. Sometimes, the results appear to be reasonably consistent; others less so. Meta-analysis enables a rigorous comparison to be made rather than focusing on a subjective 'eyeballing'. However, the technique relies on all the relevant information being available for each of the examined studies. If some crucial factors like sample size and methodology are missing, then, no comparison is feasible. Meta-analysis allows us to compare or combine results across a set of similar studies. The units of analysis in individual studies are individual observations. In meta-analysis, the units of analysis are the results of individual studies. Meta-analysis is an objective and quantitative methodology for synthesizing the previous studies and research on a particular topic into an overall finding.In meta-analysis, literature from written sources is placed in a systematic review to determine, based on previous studies, how much is the effect of one variable on another variable. Meta-analysis involves the results of studies as the unit of analysis, specifically results in the form of effect sizes. Obtaining these effect sizes does not require having access to the raw data, which are all-too-often unavailable. It is usually possible to compute these effect sizes from the data reported in papers resulting from the original, primary, or secondary analysis. Meta-analysis is a literature review to summarize the findings of various studies conducted on the same subject matter. It is used only when the examined studies are in the form of quantity studies.In this study, articles were reviewed by using a systematic review, in which topics, such as research method, used variables, and the geographical area or territory under investigation are addressed. After the systematic review, the effect size of each variable is assessed. The population of this study included almost all scientific papers with the subject of factors related to environmental crimes published between 2001 and 2021. Finally, 44 papers were selected and analyzed. For analyzing the data collected from the relevant research, the comprehensive meta-analysis software was used for meta-analysis statistical calculations after coding the data. Also, Cohen's table was applied for interpreting the effect sizes.

The results of the systematic review showed that illegal wildlife hunters and then illegal wildlife dealers were among the most frequently investigated populations in the field of environmental crimes. Most of the research related to environmental crimes had been done in African regions. The regions of East Asia, North America, and Eastern and Western Europe were in the next ranks. The results showed that the process of law enforcement, market demand, and unemployment, compared to other variables, had a significant impact on environmental crimes.The findings revealed that the relationship between market demand and environmental crimes in the studies reviewed was positive and significant (effect size = 0.51). The relationship between unemployment and livelihoods and environmental crimes in the studies reviewed was positive and significant (effect size = 0.38) as well. These results demonstrated that the combined effects of the relationship between the process of law enforcement and environmental crimes in the reviewed studies were equivalent to 0.32, thus being positive and significant.