**2. Bryophytes and the environmental changes**

Climate change is affecting the group very deeply, in particular because they are very dependent on water, including for their sexual reproduction, as they have flagellated antherozoids. Even in environments where they are the dominant flora, such as in maritime Antarctica, species may have their occurrence threatened in the face of climate change. This is also the case of boreal areas and high mountains ecosystems [7]. Bryophytes can even be used for monitoring and as an indication of the effects of climate change on living organisms. They have even been indicated as "canaries in the coal mine" with regard to their behavior in relation to the external environment [8]. As a result, they are symbols of eternity in some cultures.

This group has very simple thalli, with leaves generally formed by only one layer of cells, stems without conductive tissues and rhizoids only one cell thick, which obtain

their nourishment directly from atmospheric humidity, from the soil or substrate where they are fixed. Many react quickly in the presence of pollutants and can be used to monitor and control them. Morphological and even genetic modifications in relation to the toxicity of polluting metals or even the stress caused by their presence can be followed, making them first-class bioindicators [9, 10]. Many species are extremely sensitive to pollutants, suffering some injuries or even resulting in the death of the entire thallus, while others are very resistant, even managing to retain pollutants, preventing them from affecting other species in the environment [11]. The reduction of pollutants in large urban centers is already being done using bryophytes in systems that filter and purify the atmospheric air with great efficiency.

There are even species that live submerged in water and that can collaborate in the removal of pollutants from these systems without suffering damage, as is the case of *Leptodyction riparium*, *Fontinalis antipyretica,* and *Scapania undulata*, among others [12, 13]. Some aquatic species are even reported as accumulating very rare chemical elements in nature such as Nd, Gd, Ho, Er, Tm, Lu, La, Ce, Sm, Eu, Tb, and Dy [14].
