A recent study at the University of California Santa Barbara analyze the use of life expectancy assessment, LCA, to prove that indeed agriculture does not necessarily always change at a constant, minimal change. A professor at UCSB by the name of Sangwon Suh stated that, “People tend to think of agricultural as an industry of the past that doesn’t change much and has environmental impacts that are more or less constant over time", which makes many producers believe that it is okay to use 20 year old data from LCA's to assess agricultural products today. Both Suh and one of his students decided to publish a paper describing what characteristics make agricultural today rather diverse, such as climate change and advancements in technology. They ran tests on four different crops: corn, wheat, soybeans, and cotton, each one being measured for their acidification, eutrophication, human health criteria, and smog formation. A large majority of the tests remained consistent to their old data, however, in corn and cotton, the ecological balance of freshwater systems, such as rivers, streams, etc. heavily declined anywhere from 50-60% per acre. GMO's and genetically modified crops that don't need as much pesticide are said to be the reason for this vast decline. Suh's research makes it clear that it is vital to understand what does and doesn't promote change in environmental impacts, and that based on what information you find, you can decide whether or not to use older LCA data, frequently change the constantly updating LCA data, and just making key decisions on how to go about the concept of the impact of agriculture.
http://www.news.ucsb.edu/2015/016027/agriculture-s-environmental-footprint
http://www.news.ucsb.edu/2015/016027/agriculture-s-environmental-footprint