ENSP101Chapter 12 – Biodiversity: Preserving Landscapes12.2 World Forests- Forests and woodlands occupy some 4 billion hectares or about 30% of the world’s land surface- Grasslands (pastures and rangelands) cover about the same percentageo Together, these ecosystems supply many essential resources, such as lumber, paper pulp, and grazing land for livestocko They also provide vital ecological services, including regulating climate, controlling water runoff, providing wildlife habitat, and purifying air and watero These biomes are also among the most heavily disturbed because they’re places thatpeople prefer to live and work- Forests are widely distributed, but the largest remaining areas are the humid equatorial regions and the cold boreal forest of high latitudeso Forest – any area where trees cover more than 10% of the lando This definition includes a variety of forest types ranging from open savannas, where trees cover less than 20% of the ground, to closed-canopy forests, in which tree crowns overlap to cover most of the groundo Among the forests of greatest ecological importance are the primeval forests that are home to much of the world’s biodiversity, ecological services, and indigenous human cultureso Sometimes called frontier, old-growth, or virgin forests, these are areas large enough and free enough from human modification that native species can live out a natural life cycle, and ecological relationships play out in a relatively normal fashiono Primary forests – forests composed primarily of native species in which there are noclearly visible indications of human activity, and ecological processes are not significantly disturbedo Globally, about 1/3 of all forests are categorized as primary forests- Wood plays a part in more activities of the modern economy than does any other commodityo Total annual world wood consumption is about 4 billion m3o International trade in wood and wood products amounts to more than $100 billion each yearo Paper pulp, the fastest growing type of forest product, accounts for nearly a 5th of all wood consumptiono Global demand for paper is increasing rapidlyo Fuel wood accounts for nearly ½ of global wood useo More than ½ of the people in the world depend on firewood or charcoal as their principal source of heating and cooking fuelo Demand for fuel wood, which is increasing at slightly less than the global populationgrowth rate, is causing severe fuel wood shortages and depleting forests in some developing areas, especially around growing citieso About 1.5 billion people have less fuel wood than they need, and many experts expect shortages to worsen as poor urban areas growBecause fuel wood is rarely taken from closed-canopy forest, however, it doesn’t appear to be a major cause of deforestationo Approximately ¼ of the world’s forests are managed for wood productiono Ideally, forest management involves scientific planning for sustainable harvests, with particular attention paid to forest regeneration Monoculture agro forestry – intensive planting of a single species; an efficient wood production approach, but one that encourages pests and disease infestations and conflict with wildlife habitat or recreation uses- Tropical forests are being cleared rapidly- There are many causes for deforestationo In Africa, forest clearing by subsistence farmers is responsible for about 2/3 of the forest destruction, but large-scale commercial logging also takes a tollo In Latin America, the largest single cause of deforestation is due to expansion of cattle ranchingo Fires destroy about 350 million hectares of forest every yearo As global climate change brings drought and insect infestations to many parts of the world, there’s a worry that forest fires may increase catastrophicallyo Biofuel production- Nearly 12% of all world forests are now in some form of protected status, but the effectiveness of that protection varies greatlyo Ironically, one measure being promoted as a way of saving tropical forest could result in more destruction of primary forests – at least in the short runo People also are working on the grassroots level to protect and restore forests in other countries- Debt-for-nature swap – forgiveness of international debt in exchange for nature protection in developing countries- Temperature forests are also threatenedo Loggingo Roadless Rule – A Clinton-era ban on logging, road building, and other development on the lands identified as deserving of wilderness protection in the Roadless Area Review and Evaluations (RARE)o A much greatest threat to temperate forests may be posed by climate change, insect infestations, and wildfires, all of which are interconnected- In the 1990s the US Forest Service began to shift its policies from a timber production focus to ecosystem management, which attempts to integrate sustainable ecological, economic, and social goals in a unified, systems approacho Some of the principles of this new philosophy include: Managing across whole landscape, watersheds, or regions over ecological time scales Considering human needs and promoting sustainable economic development and communities Maintaining biological diversity and essential ecosystem processes Utilizing cooperative institutional arrangements Generating meaningful stakeholder and public involvement and facilitating collective decision making Adapting management over time, based on conscious experimentation and routine monitoring12.2 Grasslands- After forests, grasslands are among the biomes most heavily used by humanso Because grasslands, chaparral, and open woodlands are attractive for human occupation, they frequently are converted to cropland, urban areas, or other human-dominated landscapeso Worldwide the rate of grassland disturbance each year is 3x that of tropical foresto Although they may appear to be uniform and monotonous to the untrained eye, native prairies can be highly productive and species rich- By carefully monitoring the number of animals and the condition of the range, ranchers and pastoralists (people who live by herding animals) can adjust to variations in rainfall, seasonal plant conditions, and the nutritional quality of forage to keep livestock healthy andavoid overusing any particular area- Conscientious management can actually improve the quality of the rangeo When grazing lands are abused by overgrazing – especially in arid areas – rain runs off quickly before it can soak into the