If there are some terms you can't quite recall, or a term you want to know and you are constantly exposed to several aspects of the field, it's a helpful companion book.

Allaeditor of the 2nd edition of A DICTIONARY OF EARTH SCIENCES, as well as General Editor of THE OXFORD DICTIONARY OF NATURAL HISTORY. Where terms in this book's 2nd edition appear in the 2nd edition of A DICTIONARY OF EARTH SCIENCES (which came out a year later), the latter is to be preferred.

EARTH SCIENCES provides additional cross-references for various technical terms (e.g. classes of minerals) that the ECOLOGY dictionary doesn't contain. (ECOLOGY rarely seems to contain cross-references that EARTH SCIENCES does not.) Where the definitions are not identical (which is the most common occurrence when the terms appear in both books), the differences lie in the clarification of examples, the provision of additional details, rearrangement of the order of the information for greater clarity, and (where the word is used differently for non-ecological disciplines) the provision of additional alternate meanings.

In other words, Allaeditor on that book continued cleaning up and improving any terms used in common random selection of forty didn't match *any* of the senses listed in the DICTIONARY OF EARTH SCIENCES. However, out of 75 quasi-random terms in the DICTIONARY OF ECOLOGY, 35 weren't in the DICTIONARY OF EARTH SCIENCES, so unfortunately the DICTIONARY OF ECOLOGY can't be treated as a simple subset of the larger work.

Not surprisingly, the terms found in the ECOLOGY dictionary that aren't in the EARTH SCIENCES dictionary tend to be the more 'biological' terms, e.g. "saltatory" ('leaping movement, as of crickets or grasshoppers).