> Shipbuilding - the real reason there's no new elf forests!
By this logic, elf forests were expanding in coastal regions during the Closing... There are some other factors, I would suggest. ;)
But I agree that standard human shipbuilding is tied to lumbermen floating down rafts of prime timber to the shipyards.
For my version of the City of Karse, I have woodcutters in Bacofi lands cut timber from the edges of the Troll Wood and rafting them down the Marzeel to Karse. (Actually, there is a slide for single boles involved at the Bacofi main settlement which rests on both sides of a series of rapids.) The arrival of these rafts is an annual event, a trade fair for the city and the tribesfolk along the Marzeel (who use the rafts to send down their surplus to the city).
For the Bacofi, it is both a way to aquire trade goods and to defend against the denizens of the Troll Woods. The woodcutters don't dare to enter too deep, but they keep the forests from encroaching on Bacofi pasture and fields. Woodcutting season is in Storm Season, as soon as the snows allow it (and while there still is some snow to sleigh the boles to the river).
The ship-builders of Karse also send master shipwrights to the forests to designate trees for other purposes than planking, trees with "interesting" growth. Probably accompanied by Overdruvan wives preparing new trees that can provide good angles for ribs etc.
Such specialty timber probably gets imported from the southern foothills of the Storm Mountains as well, and likely is subject to ancient as well as more recent treaties.
Other centers of ship-building will have similar ties. Rightarm Islanders and Rhigosite shipyards probably use the forests of Caladraland, Longsiland in Esrolia and the Ditali Lands for their ship-building, as they would not have to cross the troll straits with the timber rafts (that might be hauled across the Mirrorsea Bay by oared ships).
Wenelia's Newcoast probably has much to offer to enterprising shipwrights, but will involve much adventure and diplomacy to provide the optimal material.
Handra is fortunate to sit in the middle of a forest, and to have a river leading up into more forested lands. I suppose that much downriver trade travels on rafts, too. No idea where exactly the Handran shipwrights get their timber - neither Pralorela nor Tarinwood sound like pleasant places for lumberjacks, but southern Helby and the forests further down the Noshain sound like good places.
Pasos has fragmented elf forest islands in the west, presumably with some access to lumber for its navy. There might be both elf-friendly and elf-hostile lumbering. In the east, the coastal outskirts of Tarinwood sound like another likely source for timber, probably the only notable native export good of Khorst.
Loskalm has a history of more demand for timber than the neighboring elf forests are willing to part with. The Yggites had lumber rights in the fringes of Winterwood, but with Loskalm overexploiting these, they might now have overstayed their welcome in the forest, too. And upriver Janubian territories are now covered by the Kingdom of War, so no Rathorelan or Jonatelan lumber for the Loskalmi shipyards.
Safelster has two major and several minor rivers for rafting in timber to the lake cities. With rather small (but nonetheless proud) navies I don't see a major deforestation threat there.
The Pamaltelan coast has timber aplenty, and in some places it can be obtained without elf interference, too... I guess Laskal and the forested islands of Kareeshtu are the main sources of timber now the Vadeli don't raid Umathela any more. Maslo appears to have some agreement in Elamle providing them with the huge boles they need for their catamarans, or otherwise a working raiding strategy in Onlaks.
Kralorela and Teshnos have Fethlon and the Shanshan foothills as sources for their fleets.
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