TL;DR is an expression for Too Long; Didn’t Read. Hopefully, I can adequately summarize this article for you. If any errors are found, please point them out and I will quickly correct them
This meta-analysis synthesizes results from a decade of research from 50 projects, involving over 400 research groups specifically on environmental impacts, safety, biomaterials and biofuels, and risk assessment (p 15-16).
The short story: GMOs pose no more risk than conventional crops (p 16).
The long story
1. Environmental Impacts
In general public policy has taken the precautionary principle – even a remote risk of damage overrides possible benefits. Science does not work in absolutes and cannot prove 100% safety. Rather science can only identify possible risks. The overwhelming evidence shows that risk is no greater than any other crop for GMOs (p 20-23).
European rice was made resistant to fungal infection through genetic modification with no adverse effects on consumption and low risk for contamination (p 24-27). Nematodes are a difficult pest to control as there exists no targeted pesticide for them. Potatoes were altered to disallow initial entry and reproduction for nematodes with no risk to humans or other animals (p 28-33). Modified potatoes in the Andes did not pose any more risk to wildlife than conventional potato farming. In fact, because of species specific pesticides for invasive nematodes risk of damage from nonspecific pesticides is reduced. There is little risk for cross pollination with local non-GM potato and there is low risk for nematode resistance development due to the two factor resistance in the GM potato (p 34-37)
Genetic engineering is a possible alternative which takes advantage of preexisting DNA and optimizing it for a desired outcome (p 40-43). Genetically engineered plants increased microbial communication in soil to increase plant growth and reduce the need for heavy nitrogen soil (p 44-47).
The primary concern is biodiversity. These and all other studies take into account the effects on wild life flora and fauna. It is impossible to know exactly what might happen given the chaos of the universe but risk assessment shows there is probably low impact on the environment especially when comparing to current farming techniques (p 112-123).