By Ruth Bender 

BERLIN -- Bayer AG plans to invest EUR5 billion ($5.64 billion) on developing new ways to combat weeds over the next decade, as the German chemicals and pharmaceuticals giant seeks to win back trust in its business in the wake of thousands of lawsuits alleging its Roundup herbicide causes cancer.

A big legal fight over the blockbuster weedkiller -- inherited with its takeover of Monsanto Co. last year -- has plunged Bayer into one of the worst crisis in its 155 year history. The company lost the first three jury trials against plaintiffs claiming Roundup gave them non-Hodgkin lymphoma, with the highest award topping $2 billion. In response, its shares have almost halved over the past year.

While Bayer is appealing all jury verdicts so far and has vigorously defended the safety of Roundup and its active ingredient glyphosate, its announcement Friday highlights how the legal woes are forcing the company to change tact in the face of growing scrutiny.

Bayer said glyphosate would continue to play an important role in its portfolio but that it was also "committed to offering more choice for growers" by developing alternatives.

"We listened. We learned," Bayer said on its website. The company said it would cut its environmental impact by 30% by 2030 through new technologies and making weedkillers more precise, and that it would also be more transparent about the safety of its products. These measures, it said, would address questions and concerns Bayer has faced since buying Monsanto over causing illness and damaging the environment. Bayer also took out newspaper advertisements to promote its message.

Bayer has faced growing criticism over its decision to buy Monsanto. At a heated shareholder meeting in late April, some 55% of shareholders refused to endorse management's actions in the past year.

The legal battle could take years to resolve as Bayer has been adamant that it would appeal decisions and wait to see the outcome of a few more cases before considering a settlement.

Investors say the legal battle is likely to weigh on Bayer's shares until there is more clarity over how much the litigation will end up costing the company. At the moment, analysts' estimates vary widely from EUR5 billion to EUR25 billion.

Roundup and other herbicides containing glyphosate have faced growing resistance in recent years. In 2015 the International Agency for Research on Cancer, a World Health Organization unit, classified the chemical as likely having the potential to cause cancer in humans. That classification triggered the wave of lawsuits. Bayer argues hundreds of studies and regulatory decisions around the world show Roundup and glyphosate are safe when used as directed.

Still, in the U.S. -- where Roundup has become integral to farming -- Costco Wholesale Corp. recently pulled Roundup herbicides from its stores. Certain cities in California, Florida, Minnesota and elsewhere have also forbidden glyphosate weedkillers on municipal property while other farm-state lawmakers have defended the herbicides.

In Europe, several countries including France and Austria are considering phasing-out glyphosate entirely. Early this year, a French court banned a Roundup product with the ingredient, even though it still has a European Union seal of approval. A senior executive of German public rail operator Deutsche Bahn AG told a German weekly Friday that the company together with the German environment ministry would research alternatives for combating weeds along its 33,000 kilometers of tracks.

Bayer said Friday that with glyphosate's global success came "widespread use, weed resistance, and in some instances unintended misapplication."

In an effort to boost transparency, Bayer said it would invite scientists, journalists and representatives from nonprofits to participate in its efforts to secure re-registration of glyphosate in the EU -- a review likely to trigger debate about safety. The process is expected to kickoff later this year, with a vote in late 2022.

--Cristina Roca contributed to this article.

Write to Ruth Bender at Ruth.Bender@wsj.com

(END) Dow Jones Newswires

June 14, 2019 08:26 ET (12:26 GMT)