On this chilly #thicktrunktuesday, let's take a mid-winter trip to the warm Southwest desert and, to begin, play a quick guessing game. Which of these two trees do you think is older -- the 200' tall coast redwood or the squat, sprawly guy on the right? 🧵1/8 
Yes, that desert ironwood (Olneya tesota) has likely been around longer than many much larger, faster-growing redwoods. Ironwoods may not be the most impressive old-growth tree in terms of size, but often very old & important to the Sonoran desert ecosystems where they grow. 2/8
A member of the legume family, ironwoods grow on valley floors & dry washes <2,500 ft in SoCal, AZ & nw Mexico. The name comes from their remarkably dense 'iron-like' wood. One of the heaviest in the world, ironwood is so heavy that if you drop a chunk into water, it sinks! 3/8
Because of their great wood density, aging ironwoods w/cores to count annual rings is difficult. Best estimates show they are often >500 yrs & some are likely as old as 1,500 yrs. Even though most trees are rather short & may even look like saplings, many are in fact ancient. 4/8
Also known as Palo Fierro, ironwoods support a great diversity of desert wildlife, and the tree is considered a keystone species wherever it occurs. For ex: studies have shown the mere presence of ironwood can increase the # of bird species assoc w/ these habitats by >60%. 5/8
Unfortunately, ironwood populations throughout the Sonoran desert are in rapid decline, due to multiple factors -- drought/climate change, utility-scale solar development, agricultural expansion, wood-cutting for charcoal, and competition w/exotic species -- are all involved. 6/8
Ironwoods in different areas are declining for different reasons. In parts of CA's Chuckwalla Valley (west of Blythe), >75% of old trees are dead. Long-term drought & groundwater pumping are most likely causes. Once lost, ironwoods are extremely slow to recover -- if ever. 7/8
“I would not sacrifice a single living desert tree for any book ever written. One square mile of living desert is worth a hundred ‘great books’ – and one brave deed to defend it is worth a thousand.” ~Edward Abbey (Postcards from Ed, 2007)
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