Biodiversity includes genetic diversity, diversity of species, habitats, ecosystems, and even wider diversity on Earth as a coherent biosphere. The ecosystem includes all living things from viruses that are on the verge of living and inanimate world, to the more complex animals and plants. Due to good geographical location, environmental and climatic conditions, Croatia is one of the richest countries in Europe to biodiversity. At the same time, a large part of Croatia is covered in forests making them one of the most important Croatian ecosystems. Habitat loss and fragmentation are among the main reasons of losses of biodiversity in Croatia and Europe. Although among the living beings, the greatest enemy of biodiversity are humans, due to excessive use of natural resources causing extinction and disappearance of species. Biodiversity is further reduced by introducing foreign species of plants and animals for their rapid adjustment to new living conditions. The task of man is to protect the biodiversity and the preservation of ecosystems. An ecological network is focused on developing systems of valuable areas for endangered species and habitats that are functionally related. It is therefore of great importance to children develop respect and protective attitude to nature from an early age.