Tag related articles. I think we've largely completed this, barring perhaps a few untagged species articles.
Find editors who have shown interest in this subject and ask them to take a look here. We've approached everyone who's written anything about lichens in the past few years.
Ensure higher-level taxa articles (genera, families, orders, classes) have up-to-date list of constituent taxa
Convert any old-style manual taxoboxes to Template:Automatic taxoboxes. Here's a list of those in Category:Lichen that still show a taxobox rather than an automatic taxobox.Clavulinaceae is still awaiting clarification from taxon specialists.
Ensure all taxon articles have all appropriate categories (see Featured/Good content in "Showcase" tab for examples of categorisation schemes)
These include: classification cat; lichen species/genus/family/order cat; location cat(s) (for species); year described in cat; taxa named by cat(s) (if available)
Review importance and quality of existing articles
Write articles on notable lichenologists. Getting rid of all redlinks in the list of Acharius Medal winners should probably be a priority
Set up and populate categories to allow navigation by biological classification.
Update various "List of genus name" articles, many of which are very out of date or not adequately referenced (see Category:Lists of lichens for examples)
Lichen systematics – would include lichen taxonomy; there's a long and interesting history behind the scientific acceptance of the lichen as a composite organism, and how to classify such an organism. This article could outline that history, continuing up to the present-day molecular phylogenetic revolution and how that's changed systematics and our understanding of phylogenetic relationships
Sexual reproduction in lichens – both of the major lichen textbooks (Lichen Biology Nash et al. (eds.) 2008 and The Lichens Ahmadjian & Hale 1973) have meaty chapters on this very topic, so it's not like there's a lack of material to work with
Lichen resynthesis – 1500+ Google Scholar results; refers to the artificial reestablishment of lichens in under laboratory-controlled conditions by growing mycobiont and photobiont together
Lichens and air pollution – 10's of thousands of hits for this topic. Should be coordinated with above article to avoid overlap
Lichens and pedogenesis – the latter term refers to soil formation by the breakdown of rock, something saxicolous, crustose lichens are good at and a phenomenon that has been widely researched (5700+ hits on Google Scholar)
Mycophycobiosis – a symbiosis where a fungus lives in the macroscopic thallus of marine algae; technically not a lichen, but an article the encyclopedia should have and not illogical to have under the purview of this task force. See doi:10.1111/j.1095-8339.1988.tb00623.x and the French wiki article
Endolichenic fungus – a fungus that lives in the thallus of a lichen; many sources (including entire books) have been written about this topic
split out the article rock tripe (currently a redirect to genus Umbilicaria) into two articles: Umbilicaria the lichen-forming fungal genus, and "rock tripe" as a survival food. I think there's enough literature out there that the latter could become a good 1000+-word article by itself, which could then be summarized with a {{template|Main}} in the taxon article (which is anticipated to later become much larger...)
lichen microbiome – microbial communities within lichens, lots of research recently