Wiesbaden, a large city with around 270,000 inhabitants, offers extremely diverse habitats for flora and fauna. Only around a quarter of the city's area is urban, but three quarters is made up of other landscapes. Among these are partly nature-protected river and floodplain landscapes along the Rhine, agricultural land with a high proportion of fruit growing and viticulture as well as large areas of forest. Climatically, Wiesbaden is characterized by high average annual temperatures and very low rainfall. At 9.5 - 10.0 °C and 550 - 650 mm, the lower-lying districts are among the warmest areas in Hesse with the lowest precipitation. The inner city area is characterized - not least due to its long tradition as a spa and health resort town - by a high and in part very old stock of trees, numerous avenues and several parks and cemeteries, some of which are planted with exotic plants. The extensive forests of the Taunus, which border Wiesbaden to the north, reach submontane heights of up to 618 m above sea level in some places within the city limits (Hohe Wurzel).

The already relatively warm climate of the Mainz basin and the Rheingau, as well as the urban heating, favor the establishment of warmth-loving, originally Mediterranean or Pontic (southeastern European) species in the parts of the city close to the Rhine. In contrast, the forested areas of the Taunus are already significantly cooler and have more precipitation and therefore provide a habitat for animals that are characteristic of temperate latitudes or require wetland biotopes (such as amphibians). While Wiesbaden, as is generally the case in urban areas of large cities, is home to a rather large variety of species, the surrounding farmland and forest landscapes with mostly intensive use are comparatively species-poor because fallow land and ecological niches have been greatly reduced. However, Wiesbaden also has some very valuable biotopes here, such as orchards(meadow orchards) and dry, warm mountain slopes, some of which have fallen into disuse, as well as several nature reserves.

In the urban core area, many animals benefit from various favorable factors: gardens, cemeteries and parks offer protected habitats, nesting sites and food. In addition, there is a large food supply due to the throwaway society and a variety of biotopes that can develop, for example, on industrial wasteland and in "poorly" maintained gardens. This more than compensates for the undoubtedly negative aspects of urban habitats such as road traffic, pollution and the isolation of biotopes. Honey bees produce higher yields due to the large number of flowering plants, and foxes, gulls, storks, birds of prey and ravens, for example, are regularly observed on the landfill sites in the Dyckerhoff quarry due to the rich food supply. Animals such as the striking black and red-colored common fire bug are also found much more frequently in urban areas than in the countryside.

The city's permanent residents also include some exotic and rare animal species such as the unmistakable collared parakeets and the shy Aesculapian snake. There are also a large number of native animal species, including numerous endangered species. These find suitable habitats in Wiesbaden's urban area, but also benefit in many places from targeted protection and settlement measures by initiatives such as the Schierstein stork community and nature conservation associations and authorities. The Rhine and the floodplain landscapes, some of which have been renaturalized and are protected, are one reason why there are a particularly large number of birds and aquatic animals among the endangered species living in Wiesbaden.

Along the Rhine, you can often observe grey herons and the strictly protected black kites in search of food, which certainly indicates a certain abundance of fish. Even without much knowledge of the species, you will soon become aware of another special feature of Wiesbaden's wildlife: the numerous white storks, whose nests can be found particularly between Schierstein and Walluf. Storks were extinct in Wiesbaden, as in the whole of Hesse, in the course of the 20th century. Since 1972, citizens of Schierstein, who are organized in the Storchengemeinschaft Schierstein e.V., have been trying to reintroduce white storks. After initial failures, the first breeding successes were achieved in the mid-1970s. This was partly due to the generally favorable habitat, but was also based on the exchange of experience with other reintroduction projects and not least the support of Wiesbaden's public utility company (ESWE Versorgungs AG), which provided the extensive water extraction site between Schierstein and Walluf, which was not open to the public. The storks find shelter there, and there are also abundant sources of food and numerous artificial nesting sites. After an initially slow development to around nine breeding pairs in 1997, a significant increase has been observed since then, with 18 breeding pairs and around 80 individuals in 2012. Nests can now be found not only on chimneys, artificial and natural nesting sites, but also several times and visibly from afar on some electricity pylons in the Schierstein area, some of which must support several nests at once.

The reasons for the strong increase in storks, for which additional measures such as feeding and keeping flightless ground storks are no longer necessary, are still unknown. It is probably favored by the good food supply in the floodplain landscapes along the Rhine, which provides the storks with a natural livelihood.

However, there may also be other reasons, including displacement from other breeding areas.

The disappearance of some ground breeders such as the tree pipit (Anthus trivialis) and the yellow wagtail (Motacilla flava) is associated with the relatively high number of storks in a small area. Institutions responsible for bird protection are also rather critical of the settlement of storks in Schierstein because it is a population with unnatural behavior patterns and because other species are threatened or displaced.

The city's parks and high tree population provide a good habitat for numerous native bird species, as well as immigrants such as exotic parakeets and the Egyptian goose (Alopochen aegyptiacus).

Even formerly shy forest animals such as the blackbird have adapted to life in cities and colonize them extensively. Another example is the frequent occurrence of the red fox. These nocturnal animals, which mainly feed on mice, but also earthworms, fruit and, last but not least, waste, are regularly observed in urban areas, e.g. in the southern cemetery.

Other animal species, some of which have become rare in Germany and are under protection, also live in the city, such as the hazel dormouse (Muscardinus avellanarius), the small relative of the house mouse, the blue-winged damselfly (Calopteryx virgo) or the damselfly (Ischnura pumilio) as well as at least four other dragonfly species. The privet hawk moth (Sphinx ligustri), a moth that is one of the largest butterflies in Europe with a wingspan of 80 - 120 mm, also finds a habitat in Wiesbaden due to the relatively frequent privet hedges.

Domestic bats such as the grey long-eared bat (Plecotus austriacus), which has its main distribution in the warm Rhine Valley, are regularly found in Wiesbaden. These and a total of nine other bat species, some of which are rare, have been documented for Wiesbaden by the Working Group for Bat Conservation, which has been committed to the conservation of bats since 1983.

The partial study for the 2010 landscape plan emphasized the importance of orchard meadows as a particularly species-rich habitat worthy of protection, especially for wildlife. Orchard meadows are quite common in Wiesbaden and a very high diversity of species, especially of many endangered and protected species, was identified in the aforementioned study. For example, 32 different butterfly species alone were identified in an orchard area near Breckenheim. The widespread distribution of the redstart (Phoenicurus phoenicurus), which is classified as endangered and is a characteristic species of this biotope type, also underlines the importance of orchard meadows for species conservation. Their isolation is considered critical for the sustainable protection of the habitats of rare and protected species.

The numerous streams that flow down from the Taunus through forests, fields and towns to the Rhine represent another important habitat for animals. Due to acidification, intensive water use, wastewater discharge and construction, many streams have been and still are largely deprived of their ecological functions. Many streams are gradually being renaturalized by the Environment Agency and with the support of many citizens and associations committed to environmental protection. For example, the renaturation and upgrading of the part of the Wellritz Valley adjacent to the city center as a landscape park is already well advanced. In the course of the renaturation efforts, detailed studies of the fauna indicating the water quality have also been carried out in recent decades. For most streams, many indicator species for water quality such as caddisflies (Silo pallipes) or freshwater shrimps (Gammarus fossarum) were found, at least in the upper reaches. Some Red List species such as river snails (Ancylus fluviatilis) are also found in many streams. Fish populations have also been recorded, e.g. brown trout in the Dambach, Klingenbach and Goldsteinbach, as well as the three-spined stickleback on several occasions.

Reptiles and amphibians are particularly prevalent in the cooler and wooded northern parts of the city. In addition, some particularly thermophilic reptile species (wall lizard and Aesculapian snake) also find suitable habitats in warmer, lower-lying biotopes, e.g. the vineyards near Frauenstein. There is relatively reliable information on the occurrence of both reptiles and amphibians, in particular based on the results of the partial study for the land use plan with data for 2009 and a mapping from 1996/97. The most common amphibians in Wiesbaden are the grass frog (Rana temporaria) and the common toad (Bufo bufo); fire salamanders (Salamandra salamandra) are also not uncommon. As in the Rheingau, all of these species have been found almost exclusively in predominantly wooded biotopes in the Wiesbaden city area, while there have been almost no findings near the Rhine. Several newt species (Triturus spec.) with a similar distribution area are also found.

Spawning waters for several amphibian species can be found in the Goldstein Valley and other water-rich areas. Here, as in other places, attempts are being made to safeguard species diversity through active measures, such as the erection of protective fences for toad migration or the preservation of spawning waters.

Several reptile species are native to the forests of Wiesbaden. Grass snakes and slow worms are the most common, followed by the common lizard (Zootoca vivipara) and the Aesculapian snake. The sand lizard (Lacerta agilis) is very common in urban areas and areas close to the Rhine, while the wall lizard (Podarcis muralis) has mainly been found on a natural stone wall in the south-eastern part of the city and must be regarded as an endangered species.

The Taunus is home to large hunting animals and numerous other mammals. These include the red deer (Cervus elaphus), the largest wild animal in the urban area, roe deer (Capreolus capreolus), the most common European deer species, and many wild boar (Sus scrofa), which often venture into parks and gardens in search of food. Stag beetles, wildcats, smooth snakes, black and red kites, tree falcons, peregrine falcons, black storks and eagle owls are among the rare animal species that are native to the region's forests and for which the Wiesbaden-Chausseehaus forestry office has taken on regional management as part of the European nature conservation network NATURA 2000. This also includes a belt of old beech forests on the edge of the Wiesbaden urban area. In addition, there are occasional reports of lynxes, the largest cats of prey in Europe, being observed in the area of the forestry office.

The Wiesbaden-Chausseehaus forestry office has also taken over the sponsorship of the Aesculapian snake and the honey buzzard and implemented a series of measures to promote them. Forest meadows were enlarged and cleared, vegetation was removed from old quarries and small temporary bodies of water were dammed.