Population decline of other organisms has been an ongoing phenomenon since man learned how to domesticate corps. Many people, including me, is curious if the use of genetically engineered grops result in the population decline of other organism.
Genetically engineered crops are more resistant to pathogens, harsh conditions, etc. As such they have advantage over other plants in competition for resources, and thus may lead to dicrease in biodiversity. On the one hand, this is not new - any crop or animal is cultivated by human to disadvantage of its natural competitors - just thinkn of the fate suffered by weeds, or by the natural population of the areas cleared for crops. On the other hand, if the genetically modified crops are able to reproduce (which is not always the case by design), they can take over other plants even beyond the areas where they were planted. Finally, the diversity of the organisms feeding or parasitizing on the genetically modified crops declines as well, for obvious reasons.
As far as my experience goes, the issue of genetically modified crops is somewhat of a controversial subject - public fears them, while the scientists forcefully push back against these fears. Thus discussing the issue seriously is hard. Still, I would be glad to correct/complete or remove my answer, if somebody more knowledgeable in the crop science chimes in.
Genetic engineering is a process, not a product or end result. Thus, it has no direct effect on "other organisms".
Humans have been modifying organisms for tens of thousands of years. We've developed multiple techniques to do so, including selective breeding, mutagenesis, grafting, interspecies hybrids, multiploidy, "genetic engineering" and so forth. Just as with producing books, the resulting product is evaluated on its own, not by what process produced it.
What matters with a book is the words it contains, not whether they were handwritten, block printed or even carved in stone. Similarly, what matters in an ecosystem are the organisms present (and their function, much determined by their genes) and the conditions they live in, not how those organisms were created.