剑桥雅思19听力test4section4原文答案解析+文本精讲（第31题到第40题）

[01:10.16]Tree planting now dominates political and popular agendas and is often presented as an easy answer to the climate crisis, as well as a way for business corporations to offset their carbon emissions.
[01:24.72]But unfortunately, tree planting isn't as straightforward as some people think.
[01:30.74]When the wrong trees are planted in the wrong place, it can do considerably more damage than good, failing to help either people or the environment.
[01:42.18]Reforestation projects are currently being undertaken on a huge scale in many countries and
it's crucial that the right trees are selected.
[01:52.86]A mix of species should always be planted, typical
of the local natural-forest ecosystem and including rare and endangered species in order
to create a rich ecosystem.
[02:06.96]It's important to avoid non-native species that could become
invasive.
[02:12.68]Invasive species are a significant contributor to the current global biodiversity crisis and are often in competition with native species and may threaten their long-term survival.
[02:28.48]Restoring biodiversity that will maximise carbon capture is key when reforesting an area but
ideally any reforestation project should have several goals.
[02:42.90]These could include selecting
trees that can contribute to wildlife conservation improve the availability of food for the local community and maintain the stability of soil systems.
[02:56.86]Meeting as many of these goals
as possible, whilst doing no harm to local communities, native ecosystems and vulnerable species, is the sign of a highly successful tree-planting scheme.
[03:12.88]To ensure the survival and resilience of a planted forest, it's vital to use tree seeds with appropriate levels of genetic diversity: the amount of genetic variation found within a species essential for their survival.
[03:30.93]Using seeds with genetic diversity generally lowers the resilience of restored forests, which can make them vulnerable to disease and unable to adapt to climate change.
[03:46.34]Choosing the right location for reforestation projects is as important as choosing the right trees.
[03:54.54]Ultimately, the best area for planting trees would be in formerly forested areas that are in poor condition.
[04:04.11]It's better to avoid non-forested landscapes such as natural grasslands, savannas or wetlands as these ecosystems already contribute greatly to capturing carbon.
[04:18.45]It would also be advantageous to choose an area where trees could provide other benefits, such as recreational spaces.
[04:28.23]Reforesting areas which are currently exploited for agriculture should be avoided as this often leads to other areas being deforested.
[04:43.94]Large-Scale reforestation projects require careful planning.
[04:49.62]Making the right decisions about
where to plant trees depends on having the right information.
[04:57.02]Having detailed and up-to-date maps identifying high-priority areas for intervention is essential.
[05:06.70]Drone technology is a useful
tool in helping to prioritise and monitor areas of degraded forest for restoration.
[05:16.94]In Brazil, it's
being used to identify and quantify how parts of the Amazon are being devastated by human activities such as rearing cattle and illegal logging.
[05:32.40]A good example of where the right trees were picked to achieve a restored forest is in Lampang Province in Northern Thailand.
[05:42.20]A previously forested site which had been degraded through mining was reforested by a cement company together with Chiang Mai University.
[05:54.34]After spreading 60 cm of topsoil, they planted 14 different native tree species which included several species of fig.
[06:06.70]Figs are a keystone species because of the critical role they play in maintaining wildlife populations.
[06:15.36]They are central to tropical reforestation projects as they accelerate the speed of the recovery process by attracting animals and birds which act as natural seed dispersers.
[06:30.18]This helps to promote diversity through the healthy regrowth of a
wide range of plant species.
[06:38.55]Unlike the majority of fruit trees, figs bear fruit all year round,
providing a reliable food source for many species.
[06:48.77]At this site, for example, after only three rainy seasons, monkeys started visiting to eat the fig fruits, naturally dispersing seeds through defecation.
[07:01.96]Reforestation projects should always aim to make sure that local communities are consulted and involved in the decision-making process.
[07:12.95]The restoration of mangrove forests in Madagascar is an example of a project which has succeeded in creating real benefits for the community.
[07:23.98]Destruction of the mangrove forests had a terrible impact on plant and animal life, and also badly affected the fishing industry, which was a major source of employment for local people living in coastal areas.
[07:40.82]The reforestation project involved hiring local people to plant and care for the new mangrove trees.
[07:50.16]Millions of mangrove trees have now been planted which has resulted in the return of a healthy aquatic ecosystem.
[07:59.21]The mangroves also act as a defence against the increased threat of flooding caused by climate change.
[08:07.48]What's more, the local economy is more stable and thousands more Madagascans are now able to send their children to school.
[08:17.89]One other important point to consider ...