My 2003 article "Umwelt ethics" is referred to in the article Jonathan Beever and I co-wrote as a framing essay to the translation of an 1917 essay by Jakob von Uexküll. Reference:
Beever, Jonathan and Morten Tønnessen 2013. “Darwin und die englische Moral”: The Moral Consequences of Uexküll’s Umwelt Theory. Biosemiotics 6(3): 437–447 (online version published September 25 2013, DOI 10.1007/s12304-013-9180-x).
The reference is made on p. 441, in this sentence:
Following Uexküll’s lead in extending consideration to a wide host of nonhuman organisms, a small but growing number of philosophers and semioticians have begun exploring whether and to what extent Umwelt theory might inform animal and environmental ethics, the study of the scope and nature of moral value in the living world (Hoffmeyer 1995; Tønnessen 2003; Kull 2001; Champagne 2011; Beever 2012; Acampora 2013 etc.).