In 1924, he married the daughter of the botanist Heinrich Schenck, Erna Walter, who also earned her doctorate in botany from the University of Heidelberg (in 1918) and was a research assistant of Ludwig Jost.
In 1953, Walter and Erna formulated the Law of relative constancy of habitat, which states that: If the climate within the residential district or area of a plant species is changing in a particular direction, this species moves into a habitat or biotope that compensates for the climate change.
Walter acquired extraordinary merits through the collaboration with Helmut Lieth in the published work "Climate Chart World Atlas" (1960-1967).
In the final chapter of this book, he also deals with the relationship of science and art and provides an opinion on the basic questions of scientific work.
[2] In German: In English: While writing the preface of many of his books, Walter quotes: "Das Laboratorium des Ökologen ist Gottes Natur Und sein Arbeitsfeld—die ganze Welt."