Learn English – Type of subordinate clause in ‘I am happy that you are here’

In your examples, understanding and learning are both nouns. Understanding is the object of the verb encourage and it is post-modified by the prepositional phrase of science. Learning is the subject of the verb is.

There are no problems with the sentence "Due to his poor memory, Richard forgot about the appointment".

The other sentence, "Due to Richard's poor memory, he forgot about the appointment" contains a possessive antecedent (Richard's poor memory), which has offended some prescriptivists.

Wikipedia has a short entry on the possessive antecedent and why some object to it. The entire entry is reproduced below:

In English grammar, a pronoun has a possessive antecedent if its antecedent (the noun that it refers to) appears in the possessive case; for example, in the following sentence, Winston Churchill is a possessive antecedent, serving as it does as the antecedent for the pronoun him:

• Winston Churchill's history shows him to have been a good writer.

In the 1960s, some usage guides started to reject the use of possessive antecedents. These guides argue that a pronoun's antecedent cannot be a noun in a possessive construct; in this case, they contend that Winston Churchill, embedded as it is in the construct Winston Churchill's, cannot serve as the antecedent for the pronoun him. The basis for this contention is that a pronoun's antecedent must be a noun, so that if Winston Churchill's is an adjective, then a pronoun cannot refer back to it. This rule does not reflect ordinary English usage, and it is commonly ignored (intentionally or otherwise) even by those who have heard of it.

There is also a discussion of the topic by Professsor Pullum on Language Log, based on a controversy as to whether the following sentence from a question in a PSAT test contains a grammatical error or not:

Toni Morrison's genius enables her to create novels that arise from and express the injustices African Americans have endured.

You can read more about the issue by doing a search on PAP or Possessive Antecedent Proscription.