American folk-singing legend and lifelong environmentalist Pete Seeger died at the age of 94 on Monday in New York.Ever-determined to “hammer out love between my brothers and my sisters,” Seeger was the father of the modern American folk-music movement, co-writing some of the country’s most enduring classics, like “If I Had a Hammer,” “Where Have All the Flowers Gone?” and “Turn! Turn! Turn!” The avid political activist and environmentalist died of natural causes at New York-Presbyterian Hospital, his grandson, Kitama Cahill Jackson, told The New York Times.Known for his liberal politics, Seeger protested against wars from Vietnam to Iraq, and he received a prison sentence for refusing to testify in Congress about his participation in the Communist Party. Throughout his career, Seeger had a complex relationship with Israel, from visiting kibbutzim in the 1960s with his family, to singing several Hebrew songs, to allegedly “wavering” in support for the Boycott, Divestment, and Sanctions (BDS) movement toward the end of his life.Born on May 3, 1919 in Patterson, New York, Seeger was exposed to music early on, as the son of two teachers at the Juilliard School of Music. He became interested in folk music through his father, who had friends involved with the genre and who directed family friend Aaron Copland to the music of West Virginia coal miners.A key moment in Seeger’s life was when he attended a mountain dance festival in North Carolina with his father.“I lost my heart to the banjo,” Reuters quotes him as saying.After dropping out of Harvard University in 1938, Seeger met protege Woody Guthrie at a benefit concert while on the road. Seeger and Guthrie established the Almanac Singers group in the early 1940s, and in 1949 Seeger was also a founding member of the Weavers. While the Weavers had a No. 1 hit with “Good Night, Irene” and by 1952 sold more than 4 million records, the members drifted apart after being blacklisted for ties to the Communist Party.Following his refusal to answer questions before the US House of Representatives Un-American Activities Committee in 1955, Seeger was prosecuted and given a prison sentence in 1961. Although the conviction was overturned, Seeger’s career did not begin to recover until the Smothers Brothers invited him to appear on their television show in 1967.Seeger spent the next two decades performing on college campuses, at folk festivals and at political rallies. He lived in upstate New York with his three children and wife Toshi, who died in 2013. After earning a Lifetime Achievement Grammy in 1993, Seeger won a Grammy for his 1997 album Pete.A committed environmentalist throughout his life, Seeger was troubled by the state of the Hudson River, which was polluted in the 1960s with raw sewage and toxic chemicals.Announcing that he was planning to “build a boat to save the river” in 1966, the Clearwater sloop set sail three years later, in conjunction with the launch of the Clearwater organization.Since then, the vessel and the organization have provided environmental education programs and community outreach programs to youth all over the region. Among other initiatives, Clearwater has been instrumental in urging the Environmental Protection Agency to require General Electric to clean up polychlorinated biphenyls (PCBs) from the Upper Hudson River, the organization said.Also in 1966, Seeger released an album called God Bless the Grass, in which many of the songs focused on environmental issues.An obituary published in The Poughkeepsie Journal on Tuesday described Seeger as nothing less than the “wellspring” for the Hudson River Valley.Not only was Seeger’s idea to launch the sloop a “radical” idea during a time when environmental protection was still young, but his work inspired environmentalists and their organizations all over the world, the The Poughkeepsie Journal says.The musician first visited Israel in 1964 to spend time on several kibbutzim with his wife and children, JTA reported. He also visited again right before the 1967 Six Day War, performing the hit Hebrew song “Tzena, Tzena, Tzena,” which he had recorded with the Weavers in 1950, according to JTA. The Weavers version of the song, originally written by Polish immigrant to Palestine Issachar Miron in 1941, made No. 2 on the Billboard charts for 1951 – second only to another song of the Weavers, “Goodnight Irene.”In addition to performing “Tzena, Tzena, Tzena,” Seeger also recorded a version of “Dayenu,” from the Passover Haggadah, in the 1959 album Folk Songs for Young People. Seeger also performed “Hineh Ma Tov” with the Weavers in their 1963 Reunion at Carnegie Hall – Part 2 album.Israeli folk singer-songwriter Chava Alberstein has often cited Seeger as one of her inspirations, and she recalled attending his 1960s Tel Aviv concert, in an interview with American music critic Seth Rogovoy.In November 2010, Seeger performed in an online peace rally “With Earth and Each Other,” in support of the Arava Institute for Environmental Studies, despite widespread calls for him to boycott the event. At the Kibbutz Ketura-based institute, students from around the world, including Jewish and Arab Israelis, as well as Palestinians and Jordanians, partake in environmental studies and research programs.Seeger resisted the call of more than 40 organizations, led by Adalah-NY: The New York Campaign for the Boycott of Israel, to skip the event and “join the growing list of artists who have respected the Palestinian boycott call.” At the time, Arava Institute executive director David Lehrer stressed that the event was not designed to be a political rally but “to show the world that there is another side of the conflict, in which people across borders are striving to work together for the betterment of all.”The musician expressed similar sentiments prior to his performance, telling JTA that, while he could understand why someone might want to boycott a place financially, he could not understanding a boycott of dialogue.“The world will not be here in 50 years unless we learn how to communicate with each other nonviolently,” he told JTA.By March 2011, however, Adalah-NY reported that Seeger had met with representatives of the Israeli Committee Against House Demolitions and said that he supports the anti-Israel BDS movement, according to JTA.Afterwards, Seeger told JTA that while he “probably said” that, he is still learning about the Israeli-Palestinian conflict and that his “opinions waver with each piece of information” he receives.After learning about Seeger’s passing, Lehrer told The Jerusalem Post that “this is indeed a sad day” for the Arava Institute and for “all those who love folk music and believe in the power of song to change the world.” Lehrer fondly recalled visiting Seeger at his home in Cold Springs, New York in 2010, when he and his daughter enjoyed singing a few songs with the musician as well.“Pete Seeger stood for justice and for standing up for the weak and the powerless,” he said. “Mr. Seeger supported the Arava Institute because of our commitment to environmental justice in the region and because of our commitment to building bridges between people instead of walls,” Lehrer continued.“We join with the rest of the humanity in mourning the loss of an important voice for peace, sustainability and human dignity.”The founder of the Arava Institute, Prof. Alon Tal, recalled the “tremendous pressure on Pete Seeger to pull out of the virtual rally.”“But Pete refused,” said Tal, a faculty member at Ben-Gurion University’s Blaustein Institute of Desert Research, on sabbatical at Stanford University.“He sought peace in the Middle East and expected Israel to pursue peace more expeditiously, but he was not an anti-Zionist,” he added.Commending Seeger’s commitment to the environment, Tal stressed that the musician’s work to preserve natural resources must be remembered by all those working toward a more sustainable future.“Pete Seeger’s efforts, indeed unflagging efforts, to restore the Hudson River to its former glory constitutes one of the great conservation stories of recent US environmental history,” he said.Tal – who is also a banjo and fiddler player in the Arava Riders bluegrass band – said he learned to play banjo using the “Peter Seeger method.”“Pete Seeger will first and foremost be remembered as someone who popularized the social conscience in the American folk tradition,” Tal said.Crediting Seeger for transforming the five-string banjo “into an acceptable acoustic instrument and not just a marginal twanging oddity,” Tal said he appreciates that Seeger made the instrument mainstream.“Most of all he loved to sing and got a lot of us who grew up in the ‘60s to love to sing the great American folk repertoire,” Tal said. “And I will always remember that he never stopped singing Israeli folk songs like ‘Hineh Mah Tov.’ Let’s look at the entirety of his remarkable life and not this or that political statement that he might have made – and sing a song in this great man’s honor today.”David Brinn contributed to this report.