"appreciable impact" means a noticeable or significant effect or influence. It refers to something that is noticeable or important enough to make a difference or have an impact. Full definition
Similarly, you can drop a ton into education without it showing appreciable impact on outcomes for 20 years as you need a whole generation of kids to grow through that upgraded system and into the workforce, and if the economy is depressed or the new jobs aren't there then you just have a bunch of better educated people facing hardship. (politics.stackexchange.com)
It found «that the Challenged Statutes impose a real and appreciable impact on students» fundamental right to equality of education and that they impose a disproportionate burden on poor and minority students.» (educationnext.org)
With coal trains already coursing through the Lower Mainland to the much larger Westshore and Neptune terminals, it's not surprising the environmental report behind the port authority's decision found no appreciable impacts on the health of area residents. (canadianbusiness.com)