CONSERVATION – Oaks and Humans

By Frank Landis, Conservation Committee Chair & Rare Plants Chair

Happy Earth Month! Originally, I was planning a thousand-word diatribe on how global civilization isn’t taking climate change seriously enough yet. That’s certainly true for everyone who wants us to travel without worrying about our emissions.

Fortunately for all of us, I got a request in parallel with efforts by the Global Consortium for the Conservation of Oaks (GCCO). This is part of an effort to protect rare oaks, yes, globally, put on by the International Union for the Conservation of Nature (IUCN) and the Morton Arboretum. In 2020 they released a global Red List for Oaks that is available at https://mortonarb.org/app/uploads/2021/05/RedListOaks2020.pdf, and now they’re trying to do something about it. Thanks to a couple of CNPSers who saw the initial invite, I got hooked into this.

IUCN has its own rarity ranking system, but the IUCN Red List more-or-less matches being on the CRPR lists. Unfortunately, there’s not much interaction between the various American Endangered Species Acts (ESA) and the international IUCN rankings, so I’m now trying to help people who normally do IUCN understand the ins and outs of California conservation politics.

In San Diego County, there are three IUCN red-listed oaks: Cedros Island oak (Quercus cedrosensis), Engelmann oak (Q. engelmannii) and Nuttall’s scrub oak (Q. dumosa). I’m working on the latter two.

Engelmann’s oak is currently California Rare Plant Rank (CRPR) list 4, which means it’s unprotected, while Nuttall’s is a list 1B, which means it could be listed under an ESA but isn’t. The reasons for these rankings are a mix of politics and science, but the upshot is that we’re starting to consider whether Engelmann oak should be re-evaluated for list 1B status, and whether Nuttall scrub oak should be listed as threatened under the California ESA.

There are multiple reasons to re-evaluate, especially with Nuttall’s scrub oak. All known populations are isolated. If climate change makes their current redoubts uninhabitable for them, how can they move north? Millions of people have settled the areas between the surviving populations, in parks along the coast, throughout the species’ range from Baja to Santa Barbara. No scrub jay could fly acorns from park to park.

Worse, oaks are slow-growing, so if they’re having trouble reproducing or even surviving, it will take a decade, likely two or more decades, before a germinating oak seedling can grow big enough produce acorns of its own. By the time we can tell they’re in trouble, it will take a lot of time and effort to get them out of trouble. And climate change is running down the clock.

The other issue is genes, because as we all know, scrub oaks hybridize. In San Diego, a putative hybrid, Quercus X acutidens (aka acutidens, the X denotes hybrid status) is thought to be the most common scrub oak in San Diego, if it’s not a species of its own. Since Nuttall’s is undeniably a scrub oak and Engelmann’s is genetically an overgrown scrub oak, it should be no surprise that both are thought to hybridize with acutidens.

This is where some people get all knotted around genetic purity and only saving “genetically pure individuals.” I’m not in that camp, and neither are most academically trained botanists. Some organisms simply hybridize more easily than do others. This group includes oaks, ceanothus, manzanita, wheats, mustards, and yes, humans. Hexaploid bread wheat, for instance, has two genomes from the genus Aegilops (goat grass), one genome of Triticum (true wheat), and we have no trouble labeling it as Triticum aestivum.

We have to work out with oaks how much genetics matter in identity. If an oak is morphologically Nuttall’s but has acutidens chloroplasts, does it matter? (Chloroplasts are generally, though not exclusively, inherited from the mother). That’s something we have to sort out. But that’s work for the oak working groups.

While we’re doing that, you can do something important.

One big question we need to answer is whether Engelmann’s and Nuttall’s are in trouble, and you can help. This won’t be precisely a rare plant committee survey, but when I was asked to float this by CNPS, I jumped at the idea.

If you’re an iNaturalist user, we want you to learn how to identify the Engelmann oak and Nuttall’s scrub oak as best you can. Use Jepson eFlora, realizing that the size and habitat information are wrong for Nuttall’s—it can get bigger and grow on a variety of soils away from the coast. Then start recording where you find them on iNaturalist. It’s especially important for Engelmann’s, because survey records are a few years old and fires in Riverside County probably wiped a bunch of them out.

While it’s important to chart where the adults are, it’s even more important to chart where the seedlings are. If all anyone can find are a bunch of old oaks without seedlings around them, that’s a huge red flag that they’re not reproducing. Seedlings, in this case, are oaks less than about a foot tall. Most of them will be under the parents. The key point is we need people to go out with iNaturalist and locate the seedlings for us, so we know where they’re currently reproducing.

Even more important than seedlings are saplings. Saplings are about knee high to head high. They’re the true gold standard for reproduction. Oaks often have seedlings under their canopies if the tree is healthy, but oaks are shade intolerant, so those little seedlings aren’t going to grow very tall unless the parent dies and they’ve got big enough root systems to survive in the resulting gap. Typically, more than 90% of oak seedlings die. While finding seedlings is important, because it tells us that the oaks can reproduce there, finding saplings is golden, because those are where oaks are reproducing successfully.

So that’s the opportunity: go out and find Engelmann’s oaks and Nuttall’s scrub oaks and upload your finds to iNaturalist. We need you to especially look for seedlings and saplings, and we need you to check places where no one’s found any, not just revisit sites that have already been surveyed. Since this isn’t a rare plant hunt, we don’t have rights of entry, so only go where you’re legally allowed to go. The important thing is to do it, because we need those data to find out what shape both species are in.

Have fun!