Harvest without felling
Most forest products require a tree to be cut down. A few do not. In tapping, a person collects a fluid or material from a living tree, which can then keep growing and be harvested again. This makes such products appealing as a way to earn income from standing trees, though the tree must be treated with care, since every tap is a wound.
The term tapping is used loosely. Here it covers collecting resin, sap and latex by cutting or drilling into the trunk, and stripping bark for cork.
Resin from conifers
Resin is a sticky substance that many conifers produce. It flows into wounds, sealing them and discouraging insects and fungi, which is why it counts among the natural tree defenses. People harvest it by making a shallow cut or removing a strip of bark to expose the wood, then collecting the resin that oozes out in a container. Fresh cuts are typically made periodically to keep it flowing.
Resin has been used for a long time. When distilled, it yields turpentine, a solvent, and rosin, a solid used in products such as varnishes, adhesives, inks and the rosin that string players put on bows. Pines are the best-known source, and resin tapping has been a significant rural industry in a number of countries. In many places it has declined as synthetic substitutes and other sources have become available, though it persists where labor costs and supply allow. Other conifers and some broadleaved trees also yield resins and gums, and frankincense and myrrh come from other trees in dry regions of Africa and Arabia.
Sap and syrup
Sap is the water-based fluid moving inside a tree. In maples, sap rises in late winter and early spring, when nights are below freezing and days are warm, as pressure inside the wood changes with the temperature swings. The movement of water in trees is explained in the article on water transport. Collectors drill a small hole in the trunk, insert a spout and gather the sap in buckets or through tubing.
Maple sap is mostly water with a little sugar, and it must be boiled down to make syrup. A common rule of thumb is that it takes about 40 liters of sap to make 1 liter of syrup, with the ratio varying by the sugar content of the sap. Birch sap is also collected in some regions, mainly in spring, and is sometimes drunk fresh or fermented.
The tapping season depends on weather, so it is one of the activities that responds visibly to changing climate. Warming winters may shift or shorten the season in some places, though the effects are uncertain and vary by region.
Latex and rubber
Natural rubber comes from latex, a milky fluid contained in specialized vessels in the tree’s bark. The main commercial source is the rubber tree, and the harvest involves cutting a thin slice of bark in a spiral groove and collecting the latex that drips out. Tappers often work in the early morning, when the latex flows best. Rubber is mostly grown in plantations, which are managed differently from natural forests, and in some areas it is intercropped on farms. Sap and latex are not the same thing, though both are tapped. Other trees produce latex used in gum products.
Cork from the bark
Cork is a different kind of harvest. It is the thick outer bark of the cork oak, a tree native to parts of the western Mediterranean region. Harvesters carefully strip this bark in sections using hand tools, leaving the inner living layer intact. The tree then grows a new cork layer. The first harvest typically comes when the tree is a few decades old, and later harvests follow about every nine years or so, with the quality of the cork generally improving after the first couple of strippings.
Cork is light, elastic and resistant to water, which is why it is used for wine stoppers, flooring, insulation, and craft and industrial products. Cork oak woodlands are a classic example of a managed landscape that supports wildlife, as well as livestock and local communities, and they belong to the family of Mediterranean woodlands. Their value depends partly on keeping the trees healthy, so the practice encourages preserving old trees instead of clearing them.
Doing it without harming the tree
Tapping can be sustainable if done with restraint. The principal rules of thumb are shared across products.
- Tap only trees large and healthy enough. Small or stressed trees can be weakened.
- Limit the number and size of taps. Too many wounds, or too deep a wound, can cause decay, reduce growth or kill the tree.
- Give trees rest. Rotating taps or leaving years between harvests allows recovery.
- Keep tools clean and cut properly, since wounds can let in disease. Insects and fungi are always a possibility, as described in the article on forest insect pests.
- Match tapping to the season. Timing affects yield and tree health.
If these are ignored, the result is over-harvest. A tree tapped heavily may produce more for a time and then decline, and once it dies the income it provided is gone.
Livelihoods and place
Tapping suits places where people have access to standing trees but little capital. A household can derive an income from a small set of trees without a mill, and the activity often involves long-standing local knowledge, which links it to indigenous forest livelihoods. Prices fluctuate, though, and markets for resin, rubber or cork can be volatile. This is why many harvesters diversify. Products gathered from living trees belong with the wider family of non-timber products, which includes foods, fibers and medicines.