The claim "Wind farms cause more environmental impact than previously thought" holds truth, but the headline itself is a bit confusing. Initial research on wind farms has focused more on the positive impact that wind farms have and what it means for energy production, as well as the fact that wind energy, to the extent that research currently shows, is better than coal energy. This is likely where the headline's phrase "than previously thought" came from.
However, studies have also shown that wind energy has negative environmental impacts. The US Office of Energy Efficiency & Renewable Energy has a project called WINDExchange that explains how "in some circumstances, wind energy projects can negatively impact the surrounding environment and the animals who live there." They also state that understanding the impacts allows for a better screening process before the construction or implementation of wind energy to determine if that site houses animals and wildlife that would be negatively impacted.
Similarly, the US Energy Information Administration, known as the EIA, states that wind energy can have negative impacts on bird and bat populations in areas where wind farms are due to the turbine blades killing birds or bats. They also state that the US government and wind energy industry are actively researching ways to lessen the impacts on these wildlife populations.
Sources: https://windexchange.energy.gov/projects/wildlife
https://www.eia.gov/energyexplained/wind/wind-energy-and-the-environment.php
