The worlds temperate broadleaf forests are composed of a diverse and economically important group of trees that have provided humans with a wide range of both wood and non-wood products. Many of these trees (e.g. oaks, laurel, birches and mountain ash) have also become integral parts of human cultures throughout the world and have important places in folklore, mythology and religion or as symbols of bravery, valour, reliability and authority. The leaf of one temperate broad-leaved tree, the sugar maple (Acer saccharum) appears on the national flag of Canada.
Temperate broad-leaved trees are the source of many important and, in some cases, unique NWFP. They come from virtually every part of these trees: flowers, foliage, bark, sap, fruits and nuts. Other important NWFP come from organisms closely associated with these trees either as parasites, symbionts or saprophytes. Examples include edible mushrooms and products such as silk and natural dyes, which come from insects that use these trees as host material. Virtually all temperate broad-leaved trees are important, to some degree, as ornamental and landscape plants, and many are popular for the ancient art of bonsai.
The fruits and nuts of many broad-leaved temperate trees are edible and have been used as food by humans since prehistoric times. Today, many are important agricultural crops and are grown throughout the world. Examples include the pome fruits, such as apples and pears; stone fruits, such as cherries, peaches, apricots and plums; various nuts, such as almonds, English or Persian walnuts, pecans and pistachios; and olives. The edible fruits or nuts of some temperate broad-leaved trees, such as chestnuts or hazelnuts, may be grown in orchards in some regions of the world but in other areas are still gathered in the forests. Still other edible fruits and nuts, such as the fruits of mountain ash, persimmon, hawthorn, black walnuts and hickory nuts, are still gathered almost entirely from natural or planted forests. The nuts of some temperate broad-leaved trees are also important sources of edible and, in some cases, industrial grade oils. Examples are walnuts, hazelnuts, olives and oil from the Asian tung tree.
Temperate broad-leaved trees produce many NWFP that are commercially important today and are significant factors in many local and regional economies. These include wild honeys; essential oils and flavourings from the foliage; syrup and related products from maple and birch trees; cork; tannins; medicinal products; and edible nuts. Cork, the soft, spongy inner bark of Quercus suber, is a particularly interesting product because it is the only product acceptable for use as bottle stoppers in fine wines and champagne. Commercially important products from organisms closely associated with temperate broad-leaved trees include edible mushrooms, produced by fungi, and silk, produced by caterpillars feeding on the foliage of mulberry or other broad-leaved trees.
Some NWFP of temperate broad-leaved trees are of sufficient importance to be subject to grading standards and harvesting regulations. Both Canada and the United States have national standards for grading maple syrup based on colour. In the Mediterranean region, cork is graded for use as bottle stoppers and related products or for agglomerate. France, Italy and Spain have strict rules governing the harvesting and labelling of truffles, and Italy requires that truffle hunters be licensed.
The use of some non-wood forest products of temperate broad-leaved trees is expanding. The development of products from agglomerated cork in the late nineteenth century resulted in a significant expansion of the cork industry. The introduction of tung tree into the southeastern United States resulted in a significant expansion of the use of tung oil and the development of a regional paint and varnish industry. The shiitake mushroom, once a strictly Asian delicacy, is now widely cultivated in western countries. There is an increasing demand for North American maple syrup in Europe and Asia and for European truffles in the United States.
Opportunities also exist for additional expansion of certain NWFP of broad-leaved temperate trees. A potentially important enterprise is the expansion of a viable chestnut industry in the United States based on blight-tolerant or resistant varieties of chestnut, as well as development of this industry in places such as Australia, New Zealand, Argentina and Chile. Another is the expanded use of Carob and Prosopis pods as a food for human consumption. Additional opportunities include increased production of silk from wild silkworms and the development of additional edible fruits, such as the hawthorn in the southern United States.
This group of trees is also the source of many products that were important in the past but have been replaced by cheaper or more effective synthetic alternatives. The development of aniline dyes during the early part of the twentieth century, for example, provided a cheap alternative source for many natural dyes, including quercitron, which was once an important source of a bright yellow dye. Similarly, the carmine or bright red dye obtained from the oak kermes scale was first replaced by the larger, easier to rear cochineal insect and later by synthetic dyes. Gathering of the summer truffle in the United Kingdom became less profitable because of increased labour costs and their relatively small size. Beech nuts, once a popular edible nut in northeastern North America, are no longer important on a commercial scale because of their small size and the fact that they were replaced by other foods. Salicylic acid, one of the ingredients of aspirin, was once extracted from willow bark but is now produced from alternative synthetic sources. Moreover, several non-wood forest products from temperate broad-leaved trees were of great importance to primitive, aboriginal societies but are of little more than academic interest today. Examples include the use of acorns from various species of Lithocarpus and Quercus by indigenous tribes in North America and the use of birch bark for shelters, canoes, drinking cups and other products across the boreal forests of the Northern Hemisphere.
The value of many NWFP of temperate broad-leaved trees has been appreciated for thousands of years. Use of tannin from oak bark for curing hides, for example, was known by the Egyptians at least as early as 3000 BC. Silk may have been a commodity in China as early as 2600 BC. The unique properties of cork were known by the Greeks and Romans as early as 100 BC. Indigenous North American tribes used the sap of both birch and maple trees as a sweetener long before the Europeans arrived, and a permanent ink, made from oak galls, was used in Europe as early as the ninth and tenth centuries.
The use of some NWFP of temperate broad-leaved trees, on the other hand, is of relatively recent origin. For example, the use of the bark of Rhamnus purshiana as a natural laxative was not appreciated until the late nineteenth century. The same is true of the use of Ulmus rubra bark to soothe irritations.
Some uses of NWFP of temperate broad-leaved trees have resulted in overharvesting, unsustainable practices, land-use conflicts and introduction of destructive pests. These have had adverse effects on trees that are sources of non-wood products. Examples include overharvesting of oak, chestnut and tanoak for tannin in North America; overharvesting of cork oak for both cork and tannin in Mediterranean Africa and Europe; and harvesting of cascara bark in the Pacific Northwest region of the United States. Increased demand for the American matsutake mushroom by Japan has resulted in conflicts between commercial mushroom harvesters and traditional harvesting by indigenous tribes in California. Introduction of the Asian chestnut blight into both Europe and North America has had devastating effects on native chestnut forests, especially in North America, where chestnuts have almost been forgotten as a food source. Introduction of the Dutch elm disease, another Asian pathogen, into Europe and North America has had devastating effects on a favourite group of ornamental and shade trees. Gypsy moth was purposely introduced from Europe into the United States in an attempt to develop a hybrid silkworm that would feed on oaks. Instead, this insect has been responsible for defoliation of millions of hectares of broadleaf forests across eastern North America, and the area of infestation continues to expand.
There are many opportunities, worldwide, to develop or expand profitable, sustainable and environmentally sound NWFP enterprises in conjunction with economic development projects either as primary or supplemental sources of income. Obviously, the development of such an enterprise must be based on the availability of an existent forest resource or the existence and availability of sites capable of supporting tree plantations. An appreciation of NWFP or the presence of traditional uses of NWFP by local residents is a significant advantage when developing such enterprises. In addition to the potential economic benefits to be derived from development and expansion of NWFP enterprises, other factors to consider are that the management and harvesting practices are sustainable and that the harvest is compatible with other forest uses.