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.

 
 

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