#endangered trees

I'm not saying size matters, but... look at these leaves, honey.

Big Leaf Mahogany (Swietenia macrophylla) AKA Caoba

Central and South America from Mexico to Bolivia

Status: Endangered

The tecate cypress is a relict. Its tiny geographic distribution encompasses a handful of sights in southern California and northwestern Mexico. It is a holdover from a time when this region was much cooler and wetter than it is today. It owes its survival and persistence to a combination of toxic soils, a proper microclimate, and fires that burn through every 30 to 40 years. However, things are changing for the Tecate cypress and they are changing fast. The fires that once ushered in new life for isolated populations of this tree are now so intense that they may spell disaster.

The taxonomy of the Tecate cypress has undergone a few revisions since it was first described. Early work on this species suggested it was simply a variety of Cupressus guadalupensis. Subsequent genetic testing revealed that these two trees were distinct enough to each warrant species status of their own. It was then given the name Cupressus forbesii, which will probably be familiar to most folks who know it well. Work done on the Tecate cypress back in 2012 has seen it moved out of the genus Cupressus and into the genus Hesperocyparis. As far as I am concerned, whether you call it Cupressus forbesii or Hesperocyparis forbesii matters not at this point.

The Tecate cypress is an edaphic endemic meaning it is found growing only on specific soil types in this little corner of the continent. It appears to prefer soils derived from ultramafic rock. The presence of high levels of heavy metals and low levels of important nutrients such and potassium and nitrogen make such soils extremely inhospitable to most plants. As such, the Tecate cypress experiences little competition from its botanical neighbors. It also means that populations of this tree are relatively small and isolated from one another.

The Tecate cypress also relies on fire for reproduction. Its tiny cones are serotinous, meaning they only open and release seeds in response to a specific environmental trigger. In this case, its the heat of a wildfire. Fire frees up the landscape of competition for the tiny Tecate cypress seedlings. After a low intensity fire, literally thousands of Tecate cypress seedlings can germinate. Even if the parent trees burn to a crisp, the next generation is there, ready to take their place.

At least this is how it has happened historically. Much has changed in recent decades and the survival of these isolated Tecate cypress populations hangs in the balance. Fires that once gave life are now taking it. You see, decades of fire suppression have changed that way fire behaves in this system. With so much dry fuel laying around, fires burn at a higher intensity than they have in the past. What's more, fires sweep through much more frequently today than they have in the past thanks to longer and longer droughts.

Taken together, this can spell disaster for small, isolated Tecate cypress populations. Even if thousands of seedlings germinate and begin to grow, the likelihood of another fire sweeping through within a few years is much higher today. Small seedlings are not well suited to cope with such intense wildfires and an entire generation can be killed in a single blaze. This is troubling when you consider the age distributions of most Tecate cypress stands. When you walk into a stand of these trees, you will quickly realize that all are of roughly the same age. This is likely due to the fact that they all germinated at the same time following a previous fire event.

If all reproductive individuals come from the same germination event and wildfires are now killing adults and seedlings alike, then there is serious cause for concern. Additionally, when we lose populations of Tecate cypress, we are losing much more than just the trees. As with any plant, these trees fit into the local ecology no matter how sparse they are on the landscape. At least one species of butterfly, the rare Thorne's hairstreak (Callophrys gryneus thornei), lays its eggs only on the scale-like leaves of the Tecate cypress. Without this tree, their larvae have nothing to feed on.

Although things in the wild seem uncertain for the Tecate cypress, there is reason for hope. Its lovely appearance and form coupled with its unique ecology has led to the Tecate cypress being something of a horticultural curiosity in the state of California. Seeds are easy enough to germinate provided you can get them out of the cones and the trees seem to do quite well in cultivation provided competition is kept to a minimum. In fact, specimen trees seem to adapt quite nicely to California's cool, humid coastal climate. Though the future of this wonderful endemic is without a doubt uncertain, hope lies in those who care enough to grow and cultivate this species. Better management practices regarding fire and invasive species, seed collection, and a bit more public awareness may be just what this species needs.

Photo Credits: [1] [2] [3] [4] [5]

Spend any amount of time reading about tropical forests around the world and you are destined to come across mention of dipterocarp forests. If you're anything like me, your initial thought might have been something along the lines of "what the heck does that mean?" Does it describe some sort of structural aspect of the forest, or perhaps a climatic component? To my surprise, dipterocarp forests refer to any forest in which the dominant species of trees are members of the family Dipterocarpaceae. Thus, I was introduced to a group of plants entirely new to me!

The family Dipterocarpaceae is comprised of 16 genera and roughly 700 species. Its members can be found throughout the tropical regions of the world, though they hit their greatest numbers in the forests of southeast Asia and specifically Borneo. As far as habit is concerned, the dipterocarps are largely arborescent, ranging in size from intermediate shrubs to towering emergent canopy trees. If you have watched a documentary on or been to a tropical forest, it is very likely that you have seen at least one species of dipterocarp.

The dipterocarps have a long evolutionary history that stretches back to the early Triassic on the supercontinent of Gondwana. As this massive landmass proceeded to break apart, the early ancestors of this group were carried along with them. Today we can find members of this family in tropical regions of South America, Africa, and Asia. Taxonomically speaking, the family is further divided into three sub families that, to some degree, reflect this distribution.  The subfamily Monotoideae is found in Africa and Colombia, the subfamily Pakaraimoideae is found in Guyana, and the subfamily Dipterocarpoideae is found in Asia.

Biologically, the dipterocarps are quite fascinating. Some species can grow quite large. Three genera - Dryobalanops, Hopea, and Shorea - regularly produce trees of over 80 meters (260 feet) in height. The world record for dipterocarps belongs to an individual of Shorea faguetiana, which stands a whopping 93 meters (305 feet) tall! That's not to say all species are giants. Many dipterocarps live out their entire lives in the forest understory.

For species growing in seasonal environments, flowering occurs annually or nearly so. Also, for dipterocarps that experience regular dry seasons, deciduousness is a common trait. For those growing in non-seasonal environments, however, flowering is more irregular and leaves are largely evergreen. Some species will flower once every 3 to 5 years whereas others will flower once every decade or so. In such cases, flowering occurs en masse, with entire swaths of forest bursting into bloom all at once. These mast years often lead to similar aged trees that all established in the same year. Though more work needs to be done on this, it is thought that various bee species comprise the bulk of the dipterocarp pollinator guild. 

Ecologically speaking, one simply cannot overstate the importance of this family. Wherever they occur, dipterocarps often form the backbone of the forest ecosystem. Their number and biomass alone is worth noting, however, these trees also provide fruits, pollen, nectar, and habitat for myriad forms of life. The larger dipterocarps are often considered climax species, meaning that they dominate in regions comprised of mostly primary forest. For the most part, these trees are able to take advantage of more successional habitats, however, this has been shown to be severely limited by the availability of localized seed sources. 

Since we are on the topic of regeneration, a conversation about dipterocarps would not be complete if we didn't touch on logging. These trees are massive components of tropical economies. Their wood is highly coveted for a a variety of uses I won't go into here. The point is that, on a global scale, dipterocarp forests have taken a huge hit. Many species within this family are now threatened with extinction. Logging, both legal and illegal, specifically aimed at dipterocarps has seen the destruction of millions of acres of old growth dipterocarp forests. With them goes all of the life that they support.

It's not enough to protect individual species. We need to rally behind whole ecosystem protection. Without it, we literally have nothing. Luckily there are groups like the Center For International Forestry Research and the Forest Research Institute of Malaysia that are working hard on research, conservation, and improved forestry standards in an effort to ease up on the detrimental practices currently in place. Still, these efforts are not enough either. Without the care, concern, and most important, the funding from folks like us, little can be done to stop the tide. That is why supporting land conservation agencies is one of the most powerful things we can do for this planet and for each other. 

Some great land conservation organizations worth supporting:

The Rainforest Trust - https://www.rainforesttrust.org/

The Nature Conservancy - http://bit.ly/2B0hFm

The Rainforest Alliance - https://www.rainforest-alliance.org/

Photo Credits: [1] [2] [3] [4]