The review is interesting. It integrates different aspects of an issue that is complex. It mixes agronomic issues with regulatory or patent issues that should be separated. This complexity is demonstrated by the fact that the conclusions are very general and I do not think that it adds much to an already difficult debate.

The review fits with the existing evidence. In fact, it is based on it. The most debatable aspects are that some of the analyses, such as the effects of deforestation, are not a direct consequence of genetically modified (GM) varieties. In fact, they also occur in crops where there are no GM varieties, such as rice or wheat.

The debate is how do we produce enough food for a growing population with large pockets of malnutrition in an environment that must reduce the use of water and soil and have less impact on the environment. Genetic modifications in general terms are an indispensable tool to find solutions to these essential questions. In each case, we must try to find the best solution and this is not easy, especially if there is a polarized debate.

The work of Noack et al. is a comprehensive review of the large-scale effects of the incorporation of GMO [genetically modified organism] crops on the environment, biodiversity, agricultural practices and human health. Their most outstanding value is that they study not the results of one-off experiments, such as those carried out in the mandatory evaluation of GMOs prior to authorization for their use, but the results on a regional, national, and even global scale of the adoption of these crops over the last 30 years. This allows them to analyze both direct and indirect effects, resulting from modifications on cropping systems, pesticide use, changes in crop costs and benefits, and the health of populations not directly involved in GMO farming practices. 

It is important to keep in mind that the use of GMO crops is very uneven, both geographically (there are 5 countries in which more than 50% of the world production of GMO crops is concentrated), and in crops (concentrated in 4 major crops: soybean, corn, cotton and rapeseed), and, especially, in the traits that have been incorporated into those crops (tolerance to herbicides, especially glyphosate, and resistance to insect pests, essentially Bt cotton and rapeseed, by incorporating Bacillus thuringiensis toxin, which gives them resistance to different species of borer, which are lepidopterans). These genetically modified crops and traits are the ones that have been developed, and they provide great economic benefits to the large companies that commercialize these types of seeds and are the only ones that have been able to afford the high costs necessary to obtain the authorizations for the use of these genetically modified crops. 

Taking all this into account, the verdict is mixed, neither completely positive nor completely negative. The effects may be opposite depending on the type of GMO crop being analyzed, the area in which the analysis is carried out or the availability of information that allows statistically valid comparisons, since there are many variables that, in addition to the adoption of a GMO crop itself, influence its long-term consequences. For example, higher productivity and lower use of various pesticides following the planting of transgenic soybeans may result in less pressure to expand the land under cultivation in one region, with the consequent positive effect on biodiversity, but in another it may lead to an expansion of the cultivated area, with the opposite effect. Even the assessment of the impact on biodiversity may differ from one taxonomic group to another, also depending on the previous information available and the different dynamics at the ecological and evolutionary scale of the groups involved. 

A general effect of the use of GMO crops is the decrease in the number of varieties planted, with the consequent risk of a greater extension of monocultures and the potential consequences of a new threat or expansion of a pathogen or pest not previously contemplated. This greater uniformity of cultivated varieties has medium and long-term consequences that have not yet been adequately evaluated in this work. 

In summary, we could say that the effects of GMO crops are not derived from the technology used to obtain them, be it genetic modification or gene editing (technologies based on CRISPR-Cas and similar), but from consequences derived more or less directly from the large-scale adoption of crops and varieties that are very similar to each other, in a market dominated by a few players and with a very limited participation of public bodies and small and medium-sized companies. This prevents the maintenance of agronomic and biological diversity which, in the medium and long term, is the best safeguard for the development and maintenance of sustainable agriculture.