[alancalverd]

Plenty of illegal immigrants - who might be classed as invaders- arrive through the same gates on migrant visas or tourist ones- and then "overstay".

A different problem but arguably easier to solve by a reverse process. We're getting away from the subject here, but one option is to provide all citizens and legitimate visitors with an "entitlement" card for public services. Tourists and migrant workers get a time limited card. No valid card, no benefits or free NHS services.  The fun bit is that the card carries any data that you would like others to access, such as allergies, medications, emergency contact numbers, you name it. A whole other subject, perhaps.

[alancalverd]

What significant number of people can actually reduce their numbers fast enough to avoid a crisis?

You miss the point. You can't avoid climate change, but within a defensible geographical area you can mitigate its effect by reducing the population to an independently sustainable level. Best choice would be an island with a temperate climate and plenty of wind and rain.

[alancalverd]

Many people think progress can be quite profitable.

So far, the profits seem to be going to Chinese solar panel, battery and nuclear reactor manufacturers, Danish windmill manufacturers, Elon Musk, HS2 consultants and lawyers, and bankers lending money on unaffordable houses.

[Petrochemicals]

2 parents 4 grand parents to look after from one worker, and possibly 2 children to support. Between a couple that is 16 people from 2 workers.

What is the retirement age in China? Assuming the worker is aged 20 - 60, it is unlikely that he will be supporting all four of his own grandparents (don't they have contributory pensions in China?). AFAIK it takes a male and a female to make a child and assuming that 20-60 year old females work, that is only one child per worker, not 2. So at the most, each worker will be supporting himself and maybe 1 - 2 others, not 16. If he has more children, he will be supporting more, not fewer, people.

it is a worst case scenario, but a good illumination. 2 (2 child policy now) young children, parents about 40 (women leaving childbearing later) and you can make the rest up yourself, births at age 16 age 20 and 30.

 One child per worker, themselves and their ancestors=8, multiplied by 2 for a family unit = 16

At present it is the flip side with 4 grandparents and 2 parents looking after 1 child

So which is true: do you need the child to look after his elders (unlikely) or are the elders supporting the child (pretty obviously)? Why would that change?

It didn't change? but an increacing birth rate economists love, even if it means that the living standard is poor, more people to labour even if the gdp per capita fails to increace, but economists would also like the pensions to come with mandatory cyanide pills.

[alancalverd]

increacing birth rate economists love

Because it means increased demand for decreasing resources, hence more money circulates, so the bankers who employ the economists are happy and everyone else suffers. The only other people who benefit from an increasing population are the sexual perverts who trade in religion: more suffering leads to more people praying for an end to suffering, or blaming members of the other religions for their fate, hence war and profit for the parasites.

"More workers" isn't a Good Thing. One of the most interesting job interviews I attended was at a Mars confectionery factory. My interviewer, the chief production engineer, said "There are 600 people working here. Our job is to reduce that to 10  whilst maintaining output." "More consumers", however, is very desirable - unless you are worried about CO2 emissions and resource depletion.

[Bored chemist]

Many people think progress can be quite profitable.

So far, the profits seem to be going to Chinese solar panel, battery and nuclear reactor manufacturers, Danish windmill manufacturers, Elon Musk, HS2 consultants and lawyers, and bankers lending money on unaffordable houses.

And if our government wasn't still focussed on oil drilling and coal mines, maybe we could get a share of that profit too.

[alancalverd]

But you need coal and oil to make solar panels, batteries, nuclear reactors, windmills, cars, railways and houses! There isn't enough reliable wind to make and process cement, steel, lithium or copper.

And governments don't determine investment - they only permit or prohibit it.

[Bored chemist]

And governments don't determine investment - they only permit or prohibit it.

or subsidise it, or tax it, or fund it.

[alancalverd]

Direct funding is rare except for weapons, and where a public service such as a railway company fails.

Subsidy was pretty much ruled out, first by Thatcher then by adherence to EU rules (which didn't apply in other countries, of course), and is now mostly limited to tax breaks on very early investment (EIS and venture capital) or bribes to foreign companies. Subsidising actual production of anything is anathema, unless the prospective factory owner happens to be related to the relevant Minister, whereupon planning restrictions magically disappear and "no contest" contracts are awarded In the Public Interest.

[Bored chemist]

Direct funding is rare except for weapons, and where a public service such as a railway company fails.

Subsidy was pretty much ruled out, first by Thatcher then by adherence to EU rules (which didn't apply in other countries, of course), and is now mostly limited to tax breaks on very early investment (EIS and venture capital) or bribes to foreign companies. Subsidising actual production of anything is anathema, unless the prospective factory owner happens to be related to the relevant Minister, whereupon planning restrictions magically disappear and "no contest" contracts are awarded In the Public Interest.

By which (possibly unique) criterion the Chinese government is better than ours.
But it's not as if either of us think much of our government.

A competent government could actually achieve something.
Even the French manage to sell us nuclear electricity.

[paul cotter]

Competent and government? hmm, I thought they were mutually exclusive.

[alancalverd]

Even the French manage to sell us nuclear electricity.

Because the rules don't apply in France.

Electricite de France S.A. (literally Electricity of France), commonly known as EDF, is a French multinational electric utility company owned by the French state.

Likewise Statoil  (now Equinor) the Norwegian state-owned fossil fuel company that invests its profits in renewables, Deutsche Bahn (ridiculously cheap fares, pay disputes all settled nationally rather than with 28 different companies...)  and so forth.

Maggie casts a long shadow, and her successors seem bent on further destruction.

[Petrochemicals]

Maggie casts a long shadow, and her successors seem bent on further destruction.

What I cannot understand about Margaret thatcher is that she I held up as something to aspire too. Just last year Liz Truss was espousing her similarities to the late Baroness. As prime minister Ms Thatcher sold stuff for money to fund tax cuts that led to inflation and crash crippling the economy, the late 80s and early 90 are thatchers testament. Why is she held in such high regard?

[alancalverd]

Why is she held in such high regard?

The people who elect Tory Prime Ministers (which includes most media proprietors and the Director of the BBC) made a lot of money. Nobody else's opinion matters or is ever heard. For heaven's sake, man, who do you think runs this country and tells you what is good for you?

[Petrochemicals]

Why is she held in such high regard?

The people who elect Tory Prime Ministers (which includes most media proprietors and the Director of the BBC) made a lot of money. Nobody else's opinion matters or is ever heard. For heaven's sake, man, who do you think runs this country and tells you what is good for you?

But that is a minority, masses of people look at Margaret thatcher with misty eyed patriotism. Another mass look at her with distane. But for my generation, a measured summation of her reign is that she was crap.

[Bored chemist]

Just last year Liz Truss was espousing her similarities to the late Baroness

You seem to be expecting rationality from Truss.
Why?

[alancalverd]

masses of people look at Margaret thatcher with misty eyed patriotism.

Machiavelli pointed this out many years ago. The best way to ensure your popularity is to start a war. Thatcher was good at picking enemies she could defeat, and was lucky with both Scargill (who had made the error of not holding a legal strike ballot, and thereby losing some of his own supporters) ) and Galtieri (who was also unpopular and needed a war).

B Liar tried the same tactic but failed because his declared casus belli was of no interest to the UK electorate, even if it had been true.

Hitler, Putin, Trump....patriotism has nothing to do with the competence of the top parasite.

[Bored chemist]

But that is a minority, masses of people look at Margaret thatcher with misty eyed patriotism.

The majority recognise Thatcher as a vandal.

[acsinuk (OP)]

You are drifting off the point that population explosion is responsible for increased CO2 emissions.
So to solve economic immigrates over running  us we need action in the countries that are causing the increase.
Why should the politicians be blamed for parents having too many children?? Well firstly they should explain to parents that they should only have the number of children that they can afford to find a job for and even build a house each for them.  No one should be allowed to abandon their children just because they are 18 and grown up.
Most of Africa, South Asia and south/central America have a problem of teenager unrest with no jobs or work blaming politicians for not expanding their economy quickly enough. But it is their own parents that are to blame. 
Politicians should however, insist that foreign donations will not undermine their economies which is happening in Africa where farmers cannot compete with free food aid that is dumped on them by mechanised nations with grain mountains to get rid of.
Further third world politicians should insist that the free maize is treated with a contraceptive to avoid pregnancies in refugee camps which is making their problem worse.
 

[Bored chemist]

Further third world politicians should insist that the free maize is treated with a contraceptive to avoid pregnancies in refugee camps which is making their problem worse.

https://en.wikipedia.org/wiki/Godwin%27s_law