Understanding Tree Bark and Its Edible Layer
To answer the question, "are there calories in bark?" one must first differentiate between the outer and inner bark. The outer bark is the hard, protective layer of a tree, full of tough fibers and bitter tannins that make it inedible and largely indigestible for humans. The valuable part, from a survival nutrition standpoint, is the cambium. This is the thin, soft, and moist layer of tissue just between the outer bark and the wood. It is this layer that is responsible for the tree's growth and transport of nutrients, which is why it contains vital carbohydrates and minerals.
The Nutritional Composition of Edible Bark
Various types of edible inner bark, particularly from certain pine, birch, and elm species, contain a significant amount of digestible starches and sugars. Research on Scots pine inner bark, for instance, found that it was rich in energy-providing carbohydrates, along with essential minerals like calcium and potassium. This was a crucial food source for the Sami people in Scandinavia, who utilized bark flour for sustenance during periods of famine.
- Carbohydrates: Provides the primary caloric energy, mainly in the form of starches and sugars.
- Dietary Fiber: Aids in digestion and provides a feeling of fullness, though it can also be difficult to process in large quantities.
- Minerals: Contains important nutrients such as calcium and potassium.
- Vitamins: Some barks, like pine inner bark, are a source of vitamin C.
Edible vs. Toxic Bark Species
Not all bark is created equal, and knowing the right species is crucial to avoid toxic varieties. A few common edible types include:
- Pine (Pinus spp.): Most pine species have edible inner bark, with the white pine often cited as one of the best-tasting.
- Birch (Betula spp.): The inner bark can be used to make flour for baking.
- Slippery Elm (Ulmus rubra): Known for its sweet, mucilaginous properties, it is one of the most palatable options.
- Aspen (Populus tremuloides): The inner bark contains starches and sugars and is edible.
Conversely, several common trees have toxic bark and should be avoided entirely, including the yew, ponderosa pine, and certain fruit tree barks.
Caloric Value Comparison: Inner Bark vs. Other Survival Foods
| Food Source | Typical Caloric Value (per pound) | Nutritional Composition | Suitability for Survival |
|---|---|---|---|
| Edible Tree Inner Bark | ~500-1000 calories | Starches, fiber, sugars, minerals (Ca, K), Vitamin C | Excellent emergency food source; high in fiber, requires preparation |
| Wild Berries | Varies significantly (e.g., 200-400 calories) | Sugars, vitamins, antioxidants | Good for quick energy; not a primary calorie source; seasonal availability |
| Acorns (Leached) | ~2,000 calories | Carbohydrates, fat, protein, vitamins, minerals | High calorie source, but requires extensive preparation to remove tannins |
| Cattail Roots | ~1,000-1,200 calories | Starches, carbohydrates, fiber | Excellent, year-round source of starch; easy to identify and harvest |
| Fish/Small Game | Varies based on species | Protein, fat | Excellent source of high-quality protein, but requires hunting/fishing skills |
How to Harvest and Prepare Edible Bark
Harvesting bark is a delicate process that should only be done in a true survival situation, as improperly done harvesting can kill the tree. Spring is the ideal time to harvest due to the high sap and nutrient content in the cambium layer.
- Select the right tree: Correctly identify a non-toxic species like pine or birch. Avoid harvesting from small or stressed trees.
- Make cuts: Carefully score the outer bark with a knife. Peel or shave off the outer bark to expose the moist, whitish inner cambium layer.
- Fillet the cambium: Use your knife to separate the thin layer of cambium from the hard, inner wood. Focus on removing thin, noodle-like strips.
- Prepare for consumption: Raw cambium can be chewy and bitter, but still edible. For better palatability and digestion, it can be:
- Boiled: Softens the fibers and can be added to soups or stews.
- Fried: Strips can be fried until crispy, much like bacon.
- Ground into flour: Dried bark can be powdered and mixed with other flours for baking.
Conclusion: Bark Provides More Than Just Survival Calories
While the caloric content of inner tree bark is substantial enough to be a viable energy source during a survival emergency, its value extends beyond just calories. The cambium layer provides essential minerals, vitamins, and fiber that can help sustain a person when no other food is available. However, it is a resource that must be harvested with care and only from non-toxic species, making foraging knowledge an essential survival skill. The practice has a rich history in indigenous and northern cultures, underscoring its historical importance as a food source. While not a pleasant meal by modern standards, the inner bark of specific trees is a reliable and calorie-rich emergency provision. For more in-depth foraging information, especially regarding potentially harmful or toxic plants, a good resource is the U.S. Forest Service research on traditional bark usage.
