WARBURG, OTTO (1859–1938), botanist and the third president of the World Zionist Organization. Born in Hamburg to a wealthy, assimilated family, *Warburg received an exclusively secular education. He completed his studies in the natural sciences in 1883 and decided to become a botanist, beginning his scientific career with studies in plant physiology and anatomy and specializing in tropical plants and plant geography and development. From 1885 to 1889 he conducted research expeditions in southern and eastern Asia and on the southeast Asian islands as far as East Australia. His observations on these expeditions provided the basis for his research work, as he discovered many hundreds of new types and species of plants. In 1892 he was appointed to a professorship at the University of Berlin. The most important of his scientific works are his books Kulturpflanzen der Weltwirtschaft (1908) and Die Pflanzenwelt (3 vols., 1916–23), a storehouse of botanical information on plant families and species, with special emphasis on their uses. A number of plant species are named after Warburg (warburgia, warburgiella, warburgina).
Warburg became a Zionist through the influence of his father-in-law, Gustav Cohen. In 1894 he was a member of the committee of *Ezra, the Berlin society of Ḥovevei Zion (see *Ḥibbat Zion). Together with his father-in-law, he joined *Herzl's supporters. He regarded the large-scale settlement of Ereẓ Israel as the basis for a Jewish state and, though a political Zionist, he was opposed to delaying settlement until the granting of a charter. Warburg also favored large-scale Jewish settlement in the countries close to Ereẓ Israel, since he believed that Ereẓ Israel would thus have a reservoir of political, economic, and demographic assistance. He participated in the attempts to settle Jews in Anatolia beginning in 1900, planning to settle there 100,000 Jews in 500 villages, and undertook the financial support of two Jewish settlements from his personal funds. From 1900 to 1906 Warburg dealt with Jewish agricultural and urban settlement in *Cyprus and encouraged the *Jewish Colonization Association (ica) in its initial steps in this venture. In 1905–06 he planned the settlement of a million Jews in Mesopotamia (now Iraq), but opposed Herzl's proposals regarding *El-Arish and refused to join the Zionist El-Arish expedition. After his first visit to Ereẓ Israel, he drew closer than ever to Herzl and became his adviser on matters pertaining to settlement, providing him with the relevant material for his utopian novel Altneuland. From the Sixth Congress (1903), at which he supported the *Uganda Scheme, Warburg became active in the Zionist Organization. At the same Congress he was elected chairman of the Palestine Commission which later became the primary factor in the settlement program of the Zionist Organization, and initiated its publication Altneuland.
Warburg's main contribution to Zionism was his role in advancing practical settlement work in the Zionist Organization. He urged the Jewish Colonization Association and the *Jewish National Fund to purchase land, and encouraged the investment of private Jewish capital in agriculture, industry, and commerce. On Warburg's initiative, the Zionist Organization established the *Palestine Office under the direction of Arthur *Ruppin in 1905, as well as the Palestine Land Development Company. He played a large part in the establishment of the experimental agricultural station at Athlit under the direction of Aaron *Aaronsohn.
After Herzl's death (1904), Warburg was elected to the Zionist Executive. He disagreed with the views of David *Wolffsohn, who remained faithful to the doctrine of political Zionism. With the emergence of the leadership of the practical Zionists, Warburg was elected president of the World Zionist Organization in 1911 and technically remained in office through World War i, until 1920, while during the war years the center of world Zionist activity moved first to Copenhagen and then to London. He was elected primarily for fostering practical settlement work in Ereẓ Israel. However, he had to cease activity of this kind completely when war broke out, and he concentrated instead on purely political efforts, e.g., by using his influence with the German Foreign Ministry to restrain Turkish persecution of the Jews in Palestine. After the war, Warburg dedicated himself to scientific work in Palestine. From 1921 he directed the agricultural research station at Rehovot, and from 1925 he also headed the botany department of The Hebrew University. During the 1930s Warburg divided his time between Palestine and Germany, due to his wife's illness. Severely ill himself, he spent his last years bedridden in Berlin, where he died a lonely death under Nazi rule. Sedeh Warburg, a moshav on the coastal plain, is named after him.
J. Thon, Otto Warburg (Heb., 1948); I. Reichert, in: Palestine Journal of Botany, Reḥovot series 2 (1938), 2–16; N. Sokolow, in: Davar (Aug. 9, 1928), 2; idem, History of Zionism, 2 (1919), index; A. Boehm, Die zionistische Bewegung, 1 (1935), index; M. Bodenheimer, Prelude to Israel (1963), 171–5, 179–83 and index.