Threats to Forests:
Climate changes directly and indirectly affect the growth and productivity of forests: directly due to changes in atmospheric carbon dioxide and climate and indirectly through complex interactions in forest ecosystems. Climate also affects the frequency and severity of many forest disturbances.
Impacts on Forest Growth and Productivity:
Many aspects of projected climate change will likely affect forest growth and productivity. Three examples are described below: increases in carbon dioxide (CO2), increases in temperature, and changes in precipitation.
Projected shifts in forest types.  The maps show current and projected forest types. Major changes are projected for many regions. For example, in the Northeast, under a mid-range warming scenario, the currently dominant maple-beech-birch forest type (red shading) is projected to be completely displaced by other forest types in a warmer future. Source: USGCRP (2009)
- Carbon dioxide is required for photosynthesis, the process by which green plants use sunlight to grow. Given sufficient water and nutrients, increases in atmospheric CO2may enable trees to be more productive.  Higher future CO2 levels could benefit forests with fertile soils in the Northeast. However, increased CO2 may not be as effective in promoting growth in the West and Southeast, where water is limited. 
- Warming temperatures could increase the length of the growing season. However, warming could also shift the geographic ranges of some tree species. Habitats of some types of trees are likely to move northward or to higher altitudes. Other species may be at risk locally or regionally if conditions in their current geographic range are no longer suitable. For example, species that currently exist only on mountaintops in some regions may die out as the climate warms since they cannot shift to a higher altitude.
- Climate change will likely increase the risk of drought in some areas and the risk of extreme precipitation and flooding in others. Increased temperatures would alter the timing of snowmelt, affecting the seasonal availability of water. Although many trees are resilient to some degree of drought, increases in temperature could make future droughts more damaging than those experienced in the past. In addition, drought increases wildfire risk, since dry trees and shrubs provide fuel to fires. Drought also reduces trees’ ability to produce sap, which protects them from destructive insects such as pine beetles.
Impacts of Disturbances:
Climate change could alter the frequency and intensity of forest disturbances such as insect outbreaks, invasive species, wildfires, and storms. These disturbances can reduce forest productivity and change the distribution of tree species. In some cases, forests can recover from a disturbance. In other cases, existing species may shift their range or die out. In these cases, the new species of vegetation that colonize the area create a new type of forest.
- Insect outbreaks often defoliate, weaken, and kill trees. For example, pine beetles have damaged more than 1.5 million acres of forest in Colorado and spruce beetles have damaged more than 2.5 million acres in Alaska. The hemlock woolly adelgid, an invasive species that is sensitive to cold weather and destroys Eastern hemlock, will likely extend its habitat north as the climate warms.  A lack of natural controls, such as predators, or pathogens, or inadequate defenses in trees, can allow insects to spread. Climate change could contribute to an increase in the severity of future insect outbreaks. Rising temperatures may enable some insect species to develop faster and expand their ranges northward. Invasive plant species can displace important native vegetation because the invasive species often lack natural predators. Climate change could benefit invasive plants, since they are generally more tolerant to a wider range of environmental conditions than are native plants.
- In recent years, wildfires consumed more than 6.25 million acres of forest in Alaska (roughly equal to the area of Massachusetts). Warm temperatures and drought conditions during the early summer contributed to this event.Climate change is projected to increase the extent, intensity, and frequency of wildfires in certain areas of the country. Warmer spring and summer temperatures, coupled with decreases in water availability, dry out woody materials in forests and increase the risk of wildfire. Fires can also contribute to climate change, since they can cause rapid, large releases of carbon dioxide to the atmosphere. 
- Hurricanes, ice storms, and wind storms can cause damage to forests. Hurricanes Rita and Katrina in 2005 damaged a total of 5,500 acres of forest. The amount of carbon released by these trees as they decay is roughly equivalent to the net amount of carbon sequestered by all U.S. forests in a single year.
Disturbances can interact with one another, or with changes in temperature and precipitation, to increase risks to forests. For example, drought can weaken trees and make a forest more susceptible to wildfire or insect outbreaks. Similarly, wildfire can make a forest more vulnerable to pests.   The combination of drought and outbreaks of beetles has damaged piñon pine forests in the Southwest.
llegal logging negatively impacts the economic and ecological systems of optimal forest management. According to the text of the 1998 G-8 meeting held in Birmingham on forest management, “illegal logging robs national and subnational governments, forest owners and local communities of significant revenues and benefits, damages forest ecosystems, distorts timber markets and forest resource assessments and acts as a disincentive to sustainable forest management. International trade in illegally harvested timber including transfer pricing, under invoicing and other illegal practices, exacerbates the problem of illegal logging.” The magnitude of illegal logging is significant. Research indicates that in the recent past over 70 per cent of timber processed in Indonesia came from illegal sources.
ILLEGAL LOGGING FACTS
- Illegal logging accounts for 50-90% of all forestry activities in key producer tropical forests, such as those of the Amazon Basin, Central Africa and Southeast Asia, and 15-30% of all wood traded globally*.
- Trade in illegally harvested timber is highly lucrative and estimated to be worth between USD $30 and USD $100 billion annually*.
- Improved enforcement of forest laws and increasing regulation of trade
in wood products is helping reduce illegal logging, but it continues to undermine legal trade and much more needs to be done to halt it.
- 40-61% of timber production in Indonesia is believed to stem from illegal logging.
- 25% of Russia’s timber exports originate from illegal logging.
- In Gabon, 70% of harvested timber is considered illegal.
Forest ecosystems are dynamic and complex. A disturbance to any part of the network can alter the balance of relationships and affect the entire ecosystem either positively or negatively. Fire is unique in that it can be either a beneficial natural process or a devastating catastrophe. For species like lodgepole pine, fire is necessary to help reduce competition and help the species release its seeds. However, climate change, drought and other conditions have caused occurrences of intense wildfire to increase, which can damage forests so badly that it takes years for them to naturally recover. Wildfire is necessary for forests, but also a threat to them, so strong policies and management are imperative to make sure wildfire is working for our forests instead of against them.
Total Wildland fires and Acres in the United States 1988–2014
Insect pests, diseases and other biotic agents have considerable impacts on forests and the forest sector. They can adversely affect tree growth and the yield of wood and non-wood products. Damage caused by forest pests can significantly reduce wildlife habitat thereby reducing local biodiversity and species richness. They can alter natural forest landscapes by decimating one or more tree species as has been observed in eastern American forests as a result of chestnut blight and throughout the Northern Hemisphere because of Dutch elm disease. Some pests have necessitated changes in management regimes often forcing forest managers to switch to alternative tree species in plantations; for example, the failed attempts in many parts of the world to establish mahogany plantations because of the presence of mahogany shoot borers (Hypsipyla spp.). Pathogens may also limit the sites on which species can be grown successfully outside their natural range as has been experienced with red band needle blight (Mycosphaerella pini) and western gall rust (Endocronartium harknessii) infecting Pinus radiata.
Forest insect pests, diseases and other pests are having significant impacts on forests worldwide. While the devastating impacts of indigenous forest pests are already recognized, those of introduced species are increasingly being recognized as well. Rapid transport, ease of travel, and free trade have facilitated the spread of pests, as evidenced by the list of transboundary species.
There is a growing trend towards adopting more sustainable forest management strategies to contain forest pests, particularly in developed countries (FAO, 2007a). This movement is related to changes in the perception and role of forests, which are increasingly valued not just for economic reasons but also for their ecological and social functions. Insect pests are the main problem reported. Disease-causing pathogens are more difficult to detect and identify and are reported less frequently. Training and expertise in pest identification and in detection of the first signs and symptoms are needed in many countries as a first line of defence against pest introductions. Monitoring and surveillance of forest pests are needed, as well as agreement on parameters by which to gather data, in particular common definitions on what constitutes a disturbance and how the data are to be collected (FAO, 2007a).
Most countries do not have reliable information on the area of forest affected by insect pests and diseases because they do not systematically monitor these variables (FAO, 2007a)
(From: http://www.fao.org/docrep/011/i0640e/i0640e00.htm, can also find list of pests and diseases, as well as country studies.)
An integral part of sustainable forest management is measures to protect forests from natural threats such as fire, insects and diseases. Increasingly, an additional and more severe threat has been affecting the forest sector worldwide – invasive species. Invasive species are any species that are non-native to a particular ecosystem and whose introduction and spread causes, or are likely to cause, socio-cultural, economic or environmental harm or harm to human health.
The increasing global movement of people and products is also facilitating the movement of alien species around the world. These species may be unintentionally introduced to new environments in shipments of food, household goods, wood and wood products, new and used tires, animal and plant products, containers, pallets, internal packaging materials and humans. In the absence of their natural predators, competitors and pathogens, they can prosper in new environments and spread at the expense of native species, affecting entire ecosystems.
(some overlapping with illegal logging, but wanted to emphasize on the land conflict here)
Deforestation is the permanent destruction of forests in order to make the land available for other uses. An estimated 18 million acres (7.3 million hectares) of forest, which is roughly the size of the country of Panama, are lost each year, according to the United Nations’ Food and Agriculture Organization (FAO). Deforestation occurs around the world, though tropical rainforests are particularly targeted.
Some other statistics:
- About half of the world’s tropical forests have been cleared (FAO)
- Forests currently cover about 30 percent of the world’s land mass (National Geographic)
- Forest loss contributes between 6 percent and 12 percent of annual global
- carbon dioxide emissions (Nature Geoscience)
- About 36 football fields worth of trees lost every minute (World Wildlife Fund (WWF)
There are many causes of deforestation. The WWF reports that half of the trees illegally removed from forests are used as fuel. Some other common reasons are:
- To make more land available for housing and urbanization
- To harvest timber to create commercial items such as paper, furniture and homes
- To create ingredients that are highly prized consumer items, such as the oil from palm trees
- To create room for cattle ranching