Ruud Vlek

Introduction

Wild animals in the city of Amsterdam, shouldn’t you look for them primarily in the City’s Zoo? However, what do we know of the wild fauna of our inner city’s biotopes, outside the cages of the Artis Zoo? About that we have a very fragmented knowledge indeed.

Cities, and certainly inner cities, seem to be very poor in animal life, because due to human overcrowding and few green areas they provide for many species no attractive place for reproduction and food supply. Only the true city birds, successfully following and adapting to human cultures and practices, are abundant because they virtually lack natural enemies in these city environments. At closer look, however, there exists an impressive diversity of wild animals in the inner city of Amsterdam. This is caused by a great variety of urban biotopes, which exist together and supplement each other, and between which there is a mutual interchange.

The biotopes available for the diverse groups of animals in the inner city are rather different of volume. Besides describing their main characteristics we have to calculate the available space for each of them. In this article we will then explore the typical and more general as well as special animal species living in these urban biotopes, as well as a number of irregular and rarer species occurring in Amsterdam’s inner city.

Urban biotopes of the inner city.

We focus in this chapter on the different biotopes in the centre of Amsterdam, actually a heavily urbanized polder area surrounded by a long drainage canal, the Singelgracht (Nassaukade/Stadhouderskade, Mauritskade) and the inner IJ-estuarium. In this area the main quarters are the late-mediaeval inner city (dating from 1300-1600), the 17th century ring of canals, and a number of old quarters where in former times tradesmen, handicraft labourers and the middle class were living: the neighbourhoods of the Jordaan and Nieuwmarkt (16th and early 17th century’s outlays), the eastern and western ‘island’ quarters neighbouring the old harbour (mid 17th century), and the Plantage, a neighbourhood for the urban middle class of that time (a late 17th and 18th century outlay). All these different parts of the centre of Amsterdam are built before 1850.

In between the dominant 17th and 18th century houses and buildings, on several localities there are some modern, high-rise buildings (in the Central Station area, at the Rembrandt- , Waterloo- and Frederiks’ squares and along main roads such as the Vijzel- and Weesper streets and in the Plantage neighbourhood).

In the Amsterdam city centre we find three main types of biotope, which are important for animals:

1. the urban waterways: the city’s canals, the river Amstel and the harbour;
2. the built-on environment (buildings, streets, house interiors);
3. public parks and private gardens.

The first is the primary biotope, which is also an important condition for animal life in the other urban biotopes. In the following paragraphs we will deal with their main characteristics and the animals that live in them.

 

Stadswater (urban waterways)

Animal life in the inner city of Amsterdam depends on three different biotopes: the city’s waterways as the primary biotope, the built-on environment with it’s micro biotopes in and around houses, and the biotope of the inner city’s greenery (parks, shrubbery, gardens).

Each of these urban biotopes has been subject to historical changes:

The urban waterways were formerly brackish to salt water areas; these waters changed into a wholly sweet water area due to the building of locks and dams in the former Zuyder Zee (1600’s, 1870, 1932). Formerly making use of the sea’s ebb and flow, which regularly brought salt water into the city, drained the city’s canals. After the closure of the urban waterways by city locks the influence of the salt-water system was at first gradually, and after the closure of the Zuyder Zee by the IJsselmeer Dam (1932) instantly reduced. This finished the habitat for salt-water species, like salt-water mollusks and fish species. After severe pollution of the city’s canals (which caused several epidemics), the city’s houses were connected onto a sewer system (in the second half of the 20th century). Finally the sewer system was separated completely from the urban waterways (a negative development for all animals living on human waste, like algae, brown rats) but it improved the sweet water quality (a positive development for diving and fish-eating waterfowl).

The built-on environment: the expansion of the inner city, in the 16th and 17th centuries with a ring of inner city quarters for the lower classes, immigrants and Jews, in the 19th century with an outside ring of quarters for a growing industrial labourforce isolated the inner city faunistically from the city’s natural environment. Recent changes in animal life are the result of urban renovation, improvement of housing standards and hygienics, and thinning of household intensity.

Public parks and private gardens: the original vegetable gardens were transformed into private recreational gardens; these private gardens were cultivated into small pockets of private semi-natural environment (especially the lush private garden blocks along the main canals). During the 19th century the 18th century geometrical garden was transformed into a romantical and more natural garden design. In the 20th century many of these garden blocks were reduced by the construction of small buildings, office extensions and parking lots. At the end of the 20th century municipal decrees forbid such use of private gardens, while they also protect old garden trees against felling. Damage of the many elms along the canals by outbreaks of the Dutch elm disease has been reduced by controlling and monitoring their parasites (Bark beetle Scolitus multistriatus).

The aquatic biotope favours the occurrence of a number of animals, not only those bound to water, but also animals in the other urban biotopes. Especially insect- and fish-eating birds are therefore colonizing these inner city biotopes and are capable to procreate in the city (for instance Grey Heron, Great Crested Grebe, Swift and House Sparrow).
Large flying insects such as beetles, butterflies, dragonflies, flies, bees and wasps are also able to penetrate into the inner city. By human and water transport even land- and water mollusks have been able to enter the city. However, bird species living at the city’s edge because they are depending for their food supply on the surrounding countryside, have been forced to follow the shifting borders of the city (Stork, Rook, Barn Swallow and House Martin). Mammals and amphibians are mostly found at the edge of the city. Nevertheless, there is a number of species in these groups of animals even occurring in inner city biotopes (6 species of bat, 2 species of rodent, 3 amphibian species). Three bird species only recently colonized the inner city of Amsterdam as a breeding bird: Great Crested Grebe, Coot and Sparrow hawk.

Due to unfavourable habitat changes a number of animal species have disappeared from the inner city in the course of time:

1. Insects: a.o. Rat flea Xenopsylla cheopsis, several species of bumble bee, Hoverfly Eristalis intricarius, Marsh ground beetle Elaphrus riparius;
2. Mollusks of salt and brackish water, such as Shipworm Teredo navalis, Lagoon cockle Cerastoderma glaucum, Sandgaper Mya arenaria, Baltic clam Macoma baltic and Blue mussel Mytilus edilus;
3. Amphibians and reptiles: Edible frog Rana esculenta, Grass snake Natrix natrix;
4. Mammals: Black rat Rattus rattus, Noctule bat Nyctalus noctula;
5. Birds: Stork, Barn owl, Tawny owl, Barn swallow and House martin, Icterine warbler and Rook.

Some of these losses can be ascribed to changes in habitat, such as the shifting city edge, the sweetening of the aquatic biotope, and the improved housing standards and hygienics. Some other species‘ populations generally decreased nationally or in the west of the Netherlands. By improved management of the available biotopes and the continous changes in them chances arised for newcomers, such as fish-eating birds and animals of older trees (insects, woodland birds, bats). Recently a number of formerly human-shy birds have colonized our inner city.

Due to the anthropogenic and natural dynamics of urban biotopes, we may expect for the future new surprises in the animal life of Amsterdam’s inner city.