What are we actually worrying about?

If the Netherlands were filled with native trees and shrubs we would not have anything to worry about. Alas, this is not the case. Native trees and shrub species are threatened in the Netherlands. What we class as native are: species that have developed and bred naturally since the last ice age or that have been bred artificially using only local material. Of the approximately 100 native species of trees and shrubs which occur in the Netherlands more than half have become rare or very rare; 7 species have (almost) disappeared.

One of the causes of their disappearance is the century long process of deforestation. Today, native trees and shrubs are mostly to be found on old forest sites, embankments, hollows, and excavated stream banks. Unfortunately these spots are often under heavy pressure, especially from expanding agricultural activities, urban expansion and extending road networks. Because of such activities much native vegetation is lost. A lesser known but not less important cause of depletion is the use of plant material from other countries. A high proportion of plant material is cultivated from relatively cheap seed imported from South and East Europe, areas with a warmer climate. This often involves species which do occur in nature here, but have different hereditary characteristics and are therefore less adapted to circumstances in the Netherlands. For example, Field maple (Acer campestre), Sloe (Prunus spinosa) and Hedgerow hawthorn (Crataegus monogyna) of Italian origin can be found with vitality problems. The depletion must be brought to a halt. Native species belong in the nature and landscape of the Netherlands. We are responsible for their survival. If a species disappears, it's gone for good. It is not only the individual species which is worth preserving, it is also the genetic variation within the species family which forms a valuable asset. By adapting to climate and environmental circumstances, a great diversity of hereditary characteristics can be found within one species. A species will flower earlier in one area than in another, or forms earlier leaves. The diversity ensures that the species is equipped to adapt and survive in different, or changed, environmental circumstances. When types which posses this hereditary characteristic are lost the basis is weakened and susceptibility for sicknesses, for example, can set in. The variation of characteristics such as flowering methods and blossoming periods also offers more possibilities for the animals which make use of them, such as the flower visiting insects. In conclusion, it can be said that variation is an enrichment for the landscape.

What can we do?

The survival of native trees and shrubs is a problem that concerns all of us. The state, municipalities, local governments, nature protection organizations, water boards, recreation management and private owners can contribute to their conservation. And there are two ways to do it.
In the first instance, by protecting forested and wooded areas that have valuable native trees and shrubs. In order to do this we must first know where these areas are. Unfortunately many of such areas are lost regularly due to ignorance of their existence. Details of the origin of trees and shrubs should be a standard feature in planning schemes and management plans, so that their value can be taken into consideration.
Secondly, by planting new woods and trees with carefully selected plant material of native origin.

How do I know if a tree or shrub is of native origin?

Absolute proof that a tree or shrub is of native origin is not available as yet. Techniques to determine and identify hereditary material are in full development. However a good estimate can be made of the probability of origin. Nothing can be seen on the tree or shrub itself which makes it obviously native. This must be judged by certain criteria according to the tree or shrub and the site in which it grows. This involves factors which can be determined by any individual. For other criteria specific (ecological) expertise is required.
The woods or wooded area must be stated as such on all topographical maps dating from 1830-1850. Research into the archives and (verbal) information from local inhabitants can provide supportive information. The tree, shrub, and plant layers should include species that are indicative of old forest. Small-leaved lime (Tilia cordata), Woodland hawthorn (Crataegus laevigata), bracken (Pteridium aquilinum), herb Paris (Paris quadrifolia) and Wood anemone (Anemone nemorosa) are examples. Additionally the site must be within the range of natural dispersion for the species and have the right soil requirements. The species should occur in comparable circumstances in the vicinity.
The tree or shrub itself should be of the wild variety. This can be seen by factors such as leaf formation and blossoms. The age of the tree is also an indication, and so is the manner of growth: the trees should make a spontaneous, uncultivated impression. Sometimes the trees have survived through centuries of coppice cultures. These criteria do not all have to be gathered at once. Indicative plants for example can be totally lacking. And there are not always old specimens available. Therefore, it is important that these criteria are always used in cohesion with each other.

Conscientious cultivation of native plant material by Bronnen?

Since 1922 seeds and cuttings have been collected from native trees and shrubs. The cultivation takes place on a contract basis at a number of nurseries. The plant material is available from Bronnen (Centre for the distribution of native woody plants). The address and telephone number of Bronnen can be found under "contact".

Research on the genetic quality of native trees and shrubs.

In 1991 the Directorate of Nature Management of the Ministry of LNV (Agriculture, Nature Management and Fisheries) initiated a project to determine "Genetic quality of native trees and shrubs". Within the framework of this project the sites of the native trees and shrubs were mapped. Since then, research has taken place in the Dutch provinces Overijssel and Gelderland (East Twente, the Achterhoek, the Gelderse Poort), Limburg, Drenthe, the Dune area, Zeeland, South Holland and parts of North Holland, Utrecht and North Brabant. The inventories were commissioned by the Ministry of LNV, the Department of Land Planning and Nature Conservation Organization, amongst others. In 1996 research by Bronnen will start in Germany (Land Nordrhein-Westfalen) and Belgium (Flanders). By mapping the valuable sites these can be better protected and used for collecting seed.