October 17, 2019

Grapes, Plums, and Pigeons



Coccoloba is a large genus of Neotropical trees and shrubs belonging to the Buckwheat Family. Two species are found as far North as Southern Florida, where they are important and distinctive components of coastal plant communities.
Sea Grape, Coccoloba uvifera, is a broad-canopied tree commonly growing in sand or very sandy soil behind the first dune line on beaches or in coastal hammocks inland from mangroves. Sometimes it can be found along the shore just inland of the high tide line. The species is both salt and drought tolerant. Depending on location, Sea Grape can grow as a medium-tall tree with a mound-like shape, or be wind- sculpted and sand-blasted into a sparser, irregular form. It can also be found as a thicket or tall groundcover that helps anchor and stabilize beaches. Its dense branches and thick foliage shelter wildlife; it’s an important nectar source for several butterfly species. Female trees bear tasty fruit, a food source for birds and mammals.  The  fully ripe fruit can be eaten by people, too. It makes excellent jam or jelly.
 


Pigeon Plum, Coccoloba diversifolia, is a medium-sized coastal tree in South Florida. It’s less salt-tolerant than Sea Grape; typically found in coastal hammocks or behind protective dunes. Pigeon Plum is narrower and smaller leaved, too. 
Pigeon Plum Foliage
Mature trees are irregularly vase-shaped, less subject to being shaped by challenging environmental conditions.As indicated by the specific name of the species, diversifolia, Pigeon Plum leaves occur in various sizes. The blooming trees attract their own suite of butterflies. 


The small “plums” are extremely sought after by many birds, most notably the White-Crowned Pigeon, Patagioenas leucocephala. The birds also consume Sea Grape fruit. Declining populations of this frugivorous wild pigeon are extremely habitat and food source sensitive, and are subjected to hunting pressure in the Caribbean.     


White Crowned Pigeon in Sea Grape


 In the U.S., this elegant bird that seems to be highly intolerant of disturbance and occurs only in extreme South Florida and the Keys. 

White-Crowned Pigeon, Patagioenas leucocephala

 

White Crowned Pigeon by John James Audubon

   

 

 

October 4, 2019

Planting Trees and the Complexities of Good Intentions

Iris atrofusca  on Negev Hillside, image by Ori Fragman-Sapir
As humans, we often treat ourselves as though we are somehow separate from the rest of Nature. Yet everything that we do connects to the greater world. The growth and migration of human populations have profoundly influenced landscapes, species composition, and ecosystem functions for thousands of years. It’s only in our contemporary period of rapidly accelerating instability and destruction that efforts at environmental mitigation and restoration are being attempted. Many solutions seem straightforward; if a forest is logged, then replant. If the burning of fossil fuels causes climatological warming, then utilize renewable energy resources. We seek elegant, simple solutions to complex problems. Sometimes, the applied fixes exacerbate the negative conditions that need correction. 
Around the world, forests are being lost to the expansion of agriculture and cattle-grazing, wood-cutting for fuel and construction, mining, and the growth of cities. Replanted trees are often utilized as a renewable resource to be harvested. The selected species don’t always replicate the previous diversity, aren’t appropriate for all the sites being replanted, or are exotics such as Eucalyptus.
Yatir Forest, image by KKL-JNF



 

 An example of unexpected results is the Yatir Forest in Israel’s Northern Negev region. This is an area where the desert and Mediterranean ecosystems meet; people have lived there for thousands of years. Unfortunately, the forest eliminates the habitat of rare dryland species. 
Yatir Forest, image by Yosef Segal
 The planted Aleppo pines, Pinus halapensis, while native to the greater geographical region, are growing at the driest limit of their range, with no natural seedling recruitment. Many adult trees have died due to increasing droughts. Measurements taken of the dark forest canopy show that it acts as a heat sink, increasing warming effects compared to the reflective, light-colored soils. When the trees die, the carbon that is stored in their wood is released back into the global environment. It’s estimated that the trees would have to grow for at least 80 years for their accumulated carbon to mitigate the warming effect of the forest canopy. It’s questionable that the pines will survive that long.

Iris atrofusca, image by Ori Fragman-Sapir
 
 
 The current biota is exquisitely attuned to the dry scrub or grassland environment that has developed with much human input over the centuries.




The new forest should correct longstanding environmental problems like overgrazing; it’s a bulwark against desertification and should mitigate the effects of the warming, drying climate.



Yatir Forest
 
Planting trees is an excellent environmental strategy, but to be effective, the local conditions and habitat of each planting site must be part of the overall plan. Effective efforts toward carbon sequestration won’t succeed when based on unsupported assumptions. Destroying existing habitats to create new ones is not a viable path to the future.