2.4 FOREST BIODIVERSITY 49 Can you give some examples of human dependency upon biodiversity? Keystone species have an extremely high impact on a particular ecosystem relative to its population. Without them, their ecosystems would be dramatically different or even disappear. ONLINE RESOURCES Biodiversity and water Canadian boreal birds to harbour: dare asilo inheritance: patrimonio keystone: fondamentale log: tronco to log: abbattere alberi, far legname pollinator: impollinatore seed disperser: dispersore di semi snag: troncone 98 BIODIVERSITY CONSERVATION The plants and animals which currently live on Earth have continued to evolve over 65 million years thanks to the richness of biodiversity, which implies interdependent relationship of living organisms and their physical environment . However, scientists believe the current huge reduction in biodiversity, mainly due to human activities, is going to compromise nature s resilience. Role of biodiversity Healthy ecosystems, which are vital to all life on Earth, provide us with clean air, fresh water, food, resources and medicine. As outlined in the 2030 Agenda, a sustainable agriculture based on the conservation and sustainable use of biodiversity, and the restoration and safeguarding of ecosystems, can prevent poverty, increase income and reduce vulnerability to external economic shocks or environmental disasters. Suitable forest management Protecting forests is key to biodiversity preservation, as they cover almost a third of the global land area and harbour most of the Earth s terrestrial biodiversity. If forests managed for timber are to help conserve biodiversity, some important steps should be taken into consideration. Since many species depend on the complex physical structure of natural forests, it is advisable to leave in place some key habitats, including mature trees, snags and decomposing logs. These play a signi cant role in the cycling of nutrients (mainly phosphorous and nitrogen) within the forest ecosystem and are important components of wildlife habitats, furnishing cover and serving as sites for feeding, reproduction and resting for many wildlife species. Ecology and forEstry Populations of keystone species should be maintained as a high priority since they provide habitats or food for pollinators and seed dispersers, such as bats and fruit-eating birds. Native tree species should be given priority over invasive alien species in forest regeneration and in the restoration of degraded lands. The fragmentation of natural forest areas, which occurs when they are used intensively, should be minimised because habitat fragmentation reduces biodiversity by 13% to 75%. Small fragments are more likely to increase the extinction of a population, and isolated fragments are less likely to be colonised after extinction. Wide extensions of a particular forest type should not be logged at the same time and ecological corridors (whether belonging to the natural landscape or created through human intervention) should be maintained. These natural habitats allow the movement of wildlife and the exchange of genetic inheritance between species, subspecies or varieties, increasing the degree of biodiversity. Through the corridors, individuals of species avoid being isolated and suffering the consequences of uctuations and environmental disturbances. The dispersion of wildlife facilitates re-colonisation and avoids local extinctions.