A microhabitat is a smaller habitat within a larger ecosystem that has different physical and biological characteristics that support some species of plants, animals and/or microbes that are not supported by the larger ecosystem. The differences from the surrounding area could be with regard to some combination of light, temperature, humidity, substrate type (e.g., the type of soil or rock), species composition and the stability of these conditions.
The sizes of microhabitats can vary greatly, with the smallest measuring just a few centimeters. Examples include puddles, areas beneath rocks and logs, and even the insides of animal mouths and intestines. Even the smallest types can play critical roles in supporting biodiversity, and thus protecting them can be vital for maintaining overall ecosystem health and resilience.
Microhabitats are formed in various ways, including from geological activity, by organisms (both living and dead), and by human activity. As examples of formation by organisms, living trees create various microhabitats in their crowns that are very different from the conditions of the area surrounding them and which can provide cover and a food source for birds and various tree-dwelling animals. They also contain various microhabitats in their bark, in holes in their trunks, and in abnormal growths which can appear on them. A rotting log from a fallen tree can likewise provide a very different microhabitat by offering shelter and moisture suitable for various specialized insects, slugs and fungi.
A very common type of microhabitat created by animals is holes burrowed into the soil, ranging from the very tiny ones created by ants to larger ones created by voles, moles, rabbits, foxes and even bears. These holes are frequently simultaneously occupied by other species of animals, plants and microbes, and by still other species after abandonment by their creators.
Examples of microhabitats resulting from human activity include cracks in paved surfaces, crawl spaces under houses, rooftops of various types (including green roofs), trees planted along streets, ornamental fish ponds, walls with climbing plants, wood piles, abandoned lots, and artificial wetlands.
Microhabitats differ from microclimates in that the latter are small areas with climatic conditions, such as temperature, moisture and wind, distinctive from the larger, surrounding area. With microclimates the emphasis is on local climatic variations, whereas the emphasis with regard to microhabitats is on the local biological conditions. There is an intimate relationship between microclimates and microhabitats, with the former being able to create the latter and visa versa.