Download
1 / 150
1.5k likes | 1.61k Views
地球科学概论. —— Geosciences. 第十五章 当代地球科学所面临 的问题. 《 地球科学概论 》: http://202.116.83.77/hope/sites/geoscience/. 第一节 人口. We are failing to confront the population explosion.
E N D
地球科学概论 ——Geosciences
第十五章 当代地球科学所面临的问题 《地球科学概论》: http://202.116.83.77/hope/sites/geoscience/
Table 6 and Figure 1 show that the area of land quality classes varies greatly among and within countries. It is interesting that Class I land only amounts to about 1% of the region’s land. By contrast, nearly half of the land area (49.5%) is occupied by land of Classes VII, VIII, and IX, which is either too cold, too wet, too steep or otherwise unsuited for sustainable grain production. Land in Classes I to III covers about 13% and constitutes the most productive arable land. It is probably correct to assume that, with the exception of a few countries such as Papua New Guinea, this land is for the most part already under cultivation. Land in Classes IV to VI has various constraints whose rectification may require substantial inputs. These lands are also susceptible to degradation. The data clearly show that Asia as a whole is endowed with land resources of predominantly inferior agricultural potential. This situation is aggravated by presumably widespread land degradation. As there are no reliable estimates of land degradation on a country by country basis available, we had to ignore this factor. Rather, our appraisal of land quality represents the inherent quality of land before human interference or natural processes adversely, or favorably, affected it.
烟台市2007年应届大中专毕业生供需洽谈会场面烟台市2007年应届大中专毕业生供需洽谈会场面
In 2005, Japan had a total population of 127.76 million. Japan's population in 2005 was the tenth largest in the world, equivalent to 2.0 percent of the global total. Its population density measured 343 persons per square kilometer, ranking it fourth among countries with a population of 10 million or more
Comparing the age structure of Japan's population, the population pyramid of 1950 shows that Japan had a standard-shaped pyramid with a broad base. However, the shape of the pyramid has changed dramatically as the birth rate and death rate have declined. In 2005, the population of elderly citizens (65 years and over) was 26.82 million, constituting 21.0 percent of the total population and marking record highs in both number and percentage terms. The speed of aging of Japan's population is much faster than in advanced Western European countries or the U.S.A. Although the population of the elderly in Japan accounted for only 7.1 percent of the total population in 1970, 24 years later in 1994, it had almost doubled in scale, to 14.1 percent. In other countries with an aged population, it took 61 years in Italy, 85 years in Sweden, and 115 years in France for the percentage of the elderly to increase from 7 percent to 14 percent of the population. These comparisons clearly highlight the rapid progress of demographic aging in Japan.
Age Pyramid of the Population of Canada, July 1, 1971 to 2006
In this animated population pyramid one can watch population change in China unfold over a 100 year period - between 1950 and 2050. For the period 1950 to 1995 the pyramid is based on population estimates of the UN Population Division; the data for 2000 to 2050 are from the most recent medium variant UN population projection. One can see how the "baby boom" generation from the 1960s and early 1970s "moves up" the age pyramid. The animation also visualizes the aging of the Chinese population, which is caused by the significant fertility decline since the mid-1970s (and the further increase in life expectancy). Within the next 3 decades the number of elderly people in China will increase massively China's Population by Age & Sex, 1950 - 2050 (population in 1000)
This population pyramid presents the female minus the male population by age. In most age groups China has a larger male than female population - according to these raw census data. Particularly, in young age groups the "surplus" in male population is substantial. This well-known phenomenon of "missing girls" is due to the strong preference for male births in the Chinese and most other Asian societies. It is believed that only boys can later keep up the family tradition. Especially the farmers want to have at least one male child for taking over the family farm.
制约人口增长的因素 • 战争 • 资源、环境 • 生活水平、健康和疾病
第二节 资源和能源 一、资源
1. 概述 （1）资源的定义 自然资源是指从自然环境中得到的，可以采取各种方式被人们使用的任何东西（联合国教科文组织）。 （2）自然资源的分类 1）按自然要素，主要可分为矿产资源、土地资源、水资源、生物资源等四类。 2）按再生性质，可分为不可再生的资源、可再生的资源两类。
（3） 资源的有限性 1）乐观派： ①随着科学技术的发展，人类可以找到足够的新资源和新能源； ②核能的利用和资源的再循环利用，等等。
2）悲观派： ①医疗技术的进步为地球上人口增长作出了贡献； ②工业的发展加快资源和能源的消耗量； ③地球上许多资源和能源都是在漫长的地质时期中形成的，是有限的和不可再生的； ④对环境的破坏不可逆的。
2. 资源的类型 （1）矿产资源 1）含义：矿产资源：埋藏于地下或分布于地表的有用矿物或元素的含量达到具有工业利用价值的矿产资源可分为金属和非金属两大类矿产。 2）矿床：①特殊地质作用（成矿作用）形成于地壳中的地质体；②符合经济技术条件要求的；③ 能为国民经济所利用的。 3）矿石：能够提取有用组分的矿物集合体，分为矿石矿物和脉石矿物两部分。 4）矿石的品位：矿石中有用组分的含量称为品位。
5）储量：在目前的经济技术条件下可以利用的矿产资源量称为储量。5）储量：在目前的经济技术条件下可以利用的矿产资源量称为储量。 6）成矿作用：使分散在地壳和上地幔中的元素相对富集而形成矿床的作用。 7）矿产资源的寻找 地表及近地表的矿产资源日益减少。
70年代中期世界总和 2010年中国需求 煤炭 32亿吨 28-30亿吨 钢 4.5亿吨 4.2-4.5亿吨 铜 700万吨 550-600万吨 铝 1300万吨 900-1100万吨 结论：中国目前主要矿产年消费量相当于20世纪70年代中期世界年消费量总和，中国需求已经改变世界。
（2）水资源 我国水资源总量为2.8万亿m3，人均2200m3左右，是世界人均水平的1/4； 水资源量在地域上分布不均，南方多，北方少，华北地区人均水资源量只有400 m3左右。 按照国际通常标准， 人均年拥有水量在2000—10000m3时，将出现干旱季节的用水问题； 人均年拥有水量在1000—2000m3时，会出现缺水问题； 人均少于1000m3时，会出现严重的缺水的水荒局面。
二、能源 1. 太阳能。直接的辐射能、间接的如风能、水能、生物能（包括现今的生物能和地质年代的生物转变而来的煤、石油、天然气等）。
煤：一种固态的可燃有机岩。是由各种泥炭等变质而成。煤：一种固态的可燃有机岩。是由各种泥炭等变质而成。 重要的动力燃料 重要的化工原料 但热量较石油低，运输不便，易造成环境污染。
石油和天然气：是一种复杂的碳氢化合物的混合物，是由有机质转化而来的（有机成因说）。石油和天然气：是一种复杂的碳氢化合物的混合物，是由有机质转化而来的（有机成因说）。 燃烧完全、发热量高、运输方便。重要的化工原料。 油气藏的形成：生、储、盖。
