Text understanding

I´ve got an important question because I don´t agree with the point of view from my teacher.
Would you be so kind and explain me the author´s view on the necessity of immigration?
The whole text: http://www.newstatesman.com/200411080019


The fewer the better
Published 08 November 2004
This is a story of two Britains and two futures. In the first Britain, the work culture dominates; the talk is of economic growth and dynamism and competing with the rest of the world. Labour is young, cheap and biddable, and driven by the urge to "succeed" - to make it in material and career terms, with the consumer goods and lifestyles to match.
The second Britain is a quieter place. The age profile is older, the values less strident and materialistic. Work is important but so are hobbies, family and community life. Cities are more spacious, roads emptier, the countryside more rural. The air and water are cleaner and there is hope of getting the weather back to normal because the planet is no longer warming so rapidly.
Which future would we prefer? Most people would plump for the second. Yet we seem to be heading for the first.
What we do not admit is that the difference between the two futures is largely one of human numbers.In September Michael Howard, the Conservative leader, pointed out that, over the next 30 years, Britain's population would grow by 5.6 million - an increase of nearly 10 per cent on the current 59 million. Immigration accounts for 85 per cent of this increase. Because population is forecast to rise, the government plans an extra 3.8 million houses in England over the next 20 years.
the government's housing plans have been a source of controversy ever since they were published. Examine this controversy in greater depth, and you will find a developing awareness of what ecologists call "carrying capacity": the balance (or lack of it) between a physical environment and the numbers it can support.
Before the start of the current immigration surge in the 1990s, Britain's population was heading for decline - If this had been allowed to continue, with no immigration, we would be down to 30 million by 2120.
Given the close association between crowding, densities, congestion and stress, and the greater distances available between people, we would also probably see less casual public aggression. And, because young people are more likely to commit crimes, the ageing of society that would result from population decline would reinforce these trends. A Britain of 30 million people would almost certainly be a kindlier, more easygoing, more socially concerned place
What would it be like to live in a country where population halved in the space of three or four generations? Environmentally, the case for population decline is unanswerable - less pollution, greater national self-sufficiency, a reduction in fossil-fuel emissions, Applied to social and economic life, this might reduce the awful sense of competitiveness that is a relatively recent feature of cultural life, for jobs, places at school or university.
Most of the argument so far, however, has focused on the perils of decline: economic and social stagnation, the decrease in the support ratio (of workers to pensioners), emerging labour shortages and so on.
More important is what happens when "immigrants" become "natives". This is the central fallacy of the demographic "time-bomb" argument. Immigrants eventually become pensioners, and pensioners keep living longer. The only way to preserve a support ratio regarded as optimal is thus to have permanently high levels of immigration - and a population permanently, indeed infinitely, growing. David Coleman, professor of demography at Oxford University, has calculated that to keep the support ratio between pensioners and those of working age at roughly current levels would require a UK population in 2100 of approximately 300 million and rising.
And what about the world as a whole? How are developing countries, presumably expected to provide the young immigrants to the UK and other western countries, supposed to support their own old people?
Even within Britain, it is hard to make a case for labour shortages when unemployment is three times the number of vacancies. It is also hard, morally at least, to argue that we should deliberately cream off the skilled and educated workers of poorer countries
The solutions to the "problems" of population decline, in fact, lie safely within the range of realistic policy options. They include: people saving more and consuming less; better labour productivity; a higher retirement age; drawing the economically inactive back into economic activity and restructuring hard-to-fill jobs to make them more attractive.
How big should Britain's population be? That depends which sums you do - but some calculations from the Optimum Population Trust suggest 20 million or fewer.