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When it comes to fighting global warming, trees have emerged as one of the most popular weapons. With nations making little progress controlling their carbon emissions, many governments and advocates have advanced plans to plant vast numbers of trees to absorb carbon dioxide from the atmosphere in an attempt to slow climate change.

If tree-planting programmes work as advertised, they could buy precious time for the world to reduce its reliance on fossil fuels and replace them with cleaner sources of energy. One widely cited 2017 study¹ estimated that forests and other ecosystems could provide more than one-third of the total CO₂ reductions required to keep global warming below 2 °C through to 2030.

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Vulnerability of biodiversity to the impacts of climate change

The present global biota has been affected by fluctuating Pleistocene (last 1.8 million years) concentrations of atmospheric carbon dioxide, temperature, precipitation, and has coped through evolutionary changes, and the adoption of natural adaptive strategies. Such climate changes, however, occurred over an extended period of time in a landscape that was not as fragmented as it is today and with little or no additional pressure from human activities. Habitat fragmentation has confined many species to relatively small areas within their previous ranges, resulting in reduced genetic variability. Warming beyond the ceiling of temperatures reached during the Pleistocene will stress ecosystems and their biodiversity far beyond the levels imposed by the global climatic change that occurred in the recent evolutionary past.Current rates and magnitude of species extinction far exceed normal background rates. Human activities have already resulted in the loss of biodiversity and thus may have affected goods and services crucial for human well-being. The rate and magnitude of climate change induced by increased greenhouse gases emissions has and will continue to affect biodiversity either directly or in combination with other drivers of change.

Links between biodiversity and climate change

There is ample evidence that climate change affects biodiversity. According to the Millennium Ecosystem Assessment, climate change is likely to become one of the most significant drivers of biodiversity loss by the end of the century. Climate change is already forcing biodiversity to adapt either through shifting habitat, changing life cycles, or the development of new physical traits.Conserving natural terrestrial, freshwater and marine ecosystems and restoring degraded ecosystems (including their genetic and species diversity) is essential for the overall goals of both the Convention on Biological Diversity and the United Nations Framework Convention on Climate Change because ecosystems play a key role in the global carbon cycle and in adapting to climate change, while also providing a wide range of ecosystem services that are essential for human well-being and the achievement of the Millennium Development Goals.Biodiversity can support efforts to reduce the negative effects of climate change. Conserved or restored habitats can remove carbon dioxide from the atmosphere, thus helping to address climate change by storing carbon (for example, reducing emissions from deforestation and forest degradation). Moreover, conserving in-tact ecosystems, such as mangroves, for example, can help reduce the disastrous impacts of climate change such as flooding and storm surges.

Ecosystem-based Adaptation

Ecosystem-based adaptation, which integrates the use of biodiversity and ecosystem services into an overall adaptation strategy, can be cost-effective and generate social, economic and cultural co-benefits and contribute to the conservation of biodiversity.Conservation and management strategies that maintain and restore biodiversity can be expected to reduce some of the negative impacts from climate change; however, there are rates and magnitude of climate change for which natural adaptation will become increasingly difficult. Options to increase the adaptive capacity of species and ecosystems in the face of accelerating climate change include:

• Reducing non-climatic stresses, such as pollution, over-exploitation, habitat loss and fragmentation and invasive alien species.
• Wider adoption of conservation and sustainable use practices including through the strengthening of protected area networks.
• Facilitating adaptive management through strengthening monitoring and evaluation systems.

Ecosystem-based adaptation uses biodiversity and ecosystem services in an overall adaptation strategy. It includes the sustainable management, conservation and restoration of ecosystems to provide services that help people adapt to the adverse effects of climate change. Examples of ecosystem-based adaptation activities include:

• Coastal defence through the maintenance and/or restoration of mangroves and other coastal wetlands to reduce coastal flooding and coastal erosion.
• Sustainable management of upland wetlands and floodplains for maintenance of water flow and quality.
• Conservation and restoration of forests to stabilize land slopes and regulate water flows.
• Establishment of diverse agroforestry systems to cope with increased risk from changed climatic conditions.
• Conservation of agrobiodiversity to provide specific gene pools for crop and livestock adaptation to climate change.

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Why
The International Panel on Climate Change foresees an increase in extreme weather events that will challenge cities, especially in developing countries. The dominant engineering approach has been to build walls, bulkheads, levees and other fortifications to minimize the effects of future storms and sea level rises. A less appreciated response is planting more trees. Studies show that increasing a city’s green area by 10% could compensate for the temperature increase caused by climate change:
vegetation helps to block shortwave radiation while also evaporating water, cooling the ambient air and creating more comfortable microclimates. Tree canopies and root systems can also reduce stormwater flows and balance nutrient loads.
What
Melbourne encourages citizens to take pride in urban greenery through its Urban Forest Strategy, consisting of over 70,000 trees. All trees are tagged on a central database: citizens can adopt a tree, name it, track its growth and carbon offset and share this data through their social networks. Each tree has its own email address which allows citizens to report defects and diseases and even send love letters.
Potential
Trees now cover 22% of Melbourne, a figure that will rise to 40% by 2040. By developing tools and processes for measuring and modelling the potential of trees to mitigate the effects of climate change, Melbourne is positioning itself as a global leader in urban forestry.

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Trees also offer a host of other benefits for cities. They provide habitat for wildlife, reduce storm-water runoff, and sequester carbon from the atmosphere, which helps to mitigate climate change. There is also a growing body of researchshowing that exposure to trees and other vegetation has a positive effect on mental health, especially for children. All of these co-benefits speak to the wisdom of greater investment in trees and urban green infrastructure such as parks and rain gardens.

The Sustainable Development Goals, which include a dedicated goal for sustainable cities, have established rising temperatures and urban air quality as urgent global issues. Both will be discussed extensively at the annual United Nations Climate Change Conference, which starts next week in Marrakech, Morocco. But these are also local issues, experienced very differently in each city – and even in each neighborhood.

As global action on climate change and sustainability moves forward, municipal leaders can take their own steps, starting with a targeted, localized, and replicable tree-planting strategy that improves the health and wellbeing of their residents. Time to get planting.
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Each year, a quarter of Europeans suffer from depression or anxiety. It costs the EU economy about €170 billion per year, according to the World Health Organization (WHO). At the same time, over 50% of Europeans are overweight, and around 23% of women and 20% of men are obese. One in three 11-year-olds in Europe are overweight or obese.

According to a new report, people living close to trees and green spaces are less likely to be obese, inactive, or dependent on anti-depressants.

Researchers at the Institute for European Environmental Policy reviewed 200 studies for Friends of the Earth Europe and reached the conclusion that being close to nature improves your health, even when controlling for other factors.

For example, it found that middle-aged men living in deprived urban areas with high amounts of green space have a 16% lower risk of dying compared with similar groups living in equally deprived areas with less greenery.

Unsurprisingly, the closer you are to nature, the more likely you are to exercise. In Denmark, people living more than 1km from a natural green environment were more likely to be obese and less likely to exercise rigorously than those living within 300m.

Nature also has a positive impact on our brains. In Spain, people living within 300m of green areas said they had better mental health. Another study found doctors in urban areas with more trees on the street tended to prescribe fewerantidepressants than those in urban areas without trees.

Access to the outdoors also improves old age. Older people are more likely to live longer if they live near walkable greenery filled public areas, found one study.

Quite simply, people are happier and have lower mental distress when they live closer to nature.

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Picture a Chinese city scene and, chances are, you’re not seeing much green. But the Liuzhou Forest City is set to challenge perceptions about urban living in the country and be a breath of fresh air – literal and metaphorical – for its 30,000 inhabitants.

The new city, being built in southern China’s mountainous Guangxi area, will bring nature to an urban setting, with over 40,000 trees and 1 million plants covering every building.

The green city follows a string of ‘vertical forest’ projects – highrise buildings swathed in green – being built around the world. But Liuzhou Forest City, set to be completed by 2020, takes things to a whole new level.

Each year the trees will absorb 10,000 tons of CO2 and 57 tons of pollutants. They should produce about 900 tons of oxygen a year, too.

The architects behind the idea, Stefano Boeri Architetti, say the plants will also decrease the average air temperature, create noise barriers and boost biodiversity by creating a habitat for birds, insects and small animals.

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The total number of animals has halved since the 1970s in what some scientists have termed the start of Earth’s sixth mass extinction. 

Biodiversity underpins life as we know it, including the air that we breathe, the food we eat and the water we drink. 

1. Without balance, ecosystems collapse

Nature provided the resources necessary for humans to emerge as the planet’s dominant species and we continue to depend on its bounty to thrive. The complex system of relationships between plants, insects and animals has held nature in balance for millions of years.

But soaring consumption has placed unprecedented strain on the planet’s resources. Human activity is disrupting whole ecosystems – as large as the Great Barrier Reef and as small as the parasites living on a crab’s shell – or causing them to disappear altogether.

Man-made problems like pollution, climate change and deforestation are threatening more species. The number of mammals listed on the International Union for Conservation of Nature’s (ICUN) Red List increased by 12% between 2006 and 2018. During the same period, endangered insect species rose by 147% and mollusks by 125%.

2. Survival of species depends on food chains 

Losing just a single link in nature’s intricate network of relationships can create a domino effect that disrupts entire food chains.

3. Loss of livelihoods

Closer to shore, mangrove forests are disappearing, along with the livelihoods of the people who depend on them. Home to thousands of marine species, birds and mammals, mangrove swamps are being cleared to create agricultural land or to build urban developments.

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Carbon dioxide (CO2) is an important heat-trapping (greenhouse) gas, which is released through human activities such as deforestation and burning fossil fuels, as well as natural processes such as respiration and volcanic eruptions. The first graph shows atmospheric CO2 levels measured at Mauna Loa Observatory, Hawaii, in recent years, with average seasonal cycle removed. The second graph shows CO2 levels during the last three glacial cycles, as reconstructed from ice cores.

The time series below shows global distribution and variation of the concentration of mid-tropospheric carbon dioxide in parts per million (ppm). The overall color of the map shifts toward the red with advancing time due to the annual increase of CO2.

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Cause:

Scientists attribute the global warming trend observed since the mid-20^th century to the human expansion of the “greenhouse effect”¹ — warming that results when the atmosphere traps heat radiating from Earth toward space.

Gases that contribute to the greenhouse effect include:

Water vapor
Methane
Nitrous oxide
Chlorofluorocarbons (CFCs)

Carbon dioxide (CO2). A minor but very important component of the atmosphere, carbon dioxide is released through natural processes such as respiration and volcano eruptions and through human activities such as deforestation, land use changes, and burning fossil fuels. Humans have increased atmospheric CO2 concentration by more than a third since the Industrial Revolution began. This is the most important long-lived “forcing” of climate change.

Some crops and other plants may respond favorably to increased atmospheric CO2, growing more vigorously and using water more efficiently. At the same time, higher temperatures and shifting climate patterns may change the areas where crops grow best and affect the makeup of natural plant communities.

Effect:

Global climate change has already had observable effects on the environment. Glaciers have shrunk, ice on rivers and lakes is breaking up earlier, plant and animal ranges have shifted and trees are flowering sooner.

The IPCC predicts that increases in global mean temperature of less than 1.8 to 5.4 degrees Fahrenheit (1 to 3 degrees Celsius) above 1990 levels will produce beneficial impacts in some regions and harmful ones in others. Net annual costs will increase over time as global temperatures increase.