Eduardo Brondizio’s observation – “We have been displacing our impact around the planet from frontier to frontier. But we are running out of frontiers” – is crucial (Humanity facing ‘urgent threat’ from loss of Earth’s natural life, 7 May). This frontier-based structure of thought, in which there is always a beyond, an outside, a domain of otherness, underpins the dichotomies of class and hence of economics (capital and labour); of race, religion and migration; of gender and sexuality; as well as that of ecology. In every sphere, the uncivilised, untamed, more “natural” partner is positioned for exploitation and subordination. This is the basic structure underlying capitalism, but probably goes back much further to the beginnings of agriculture, when the land was first “tamed”.

Its time is up. We have reached the final frontier and there is no longer any outside. The very concept of “nature” is misleading, since it positions human beings over and against something different called the natural world, and which therefore can be conceptualised as providing us with “services”. The concept should be junked.

Richard Middleton

Crossmichael, Dumfries and Galloway

• There is a strong case for dating the start of the Anthropocene to 1950, since which time a million species have become threatened; 1950 coincides with the growth of international travel, leading to the introduction of alien species into vulnerable populations which then collapse. Back in 1950, world population was one-third of its current level. A combination of antibiotics, vaccination programmes and ineffective family planning have seen human numbers rocket past 7 billion, and they are still rising. Finally the demands of humanity have led to deforestation and widespread loss of habitat in every part of the globe.

It is entirely appropriate that the UN and other institutions produce reports documenting the disappearance and decline of most species on Earth. But they will have no impact at all unless they are accompanied by measures to limit human numbers.

Dr Robin Russell-Jones

Chair, Help Rescue the Planet

• Obviously there are many uncomfortable changes we humans are going to have to make in our attempts to rectify our sorry situation, but a very simple, painless and cheap way of making some improvement to our biodiversity is to cease our ever-increasing manicuring of hedgerows and verges. In Sweden, there is legislation to forbid verge-cutting until October; why not here? While many of our remedies to alleviate the situation are costly, this change would actually save money.

Judith Wright

Darwen, Lancashire

• Climate change is the greatest threat facing the countryside. From prolonged heatwaves and moorland wildfires to severe and more frequent flooding, our countryside is under severe pressure from the impact of climate breakdown – but it will also provide many of the solutions.

It will take a cross-departmental approach to ensure reaching a net-zero target for greenhouse gas emissions is the top priority for all ministers (Emissions must stop by 2050, UK advisers say, 2 May). But by prioritising policies and funding that will see better land use across the countryside, dramatically reduce emissions from agriculture and halt the degradation of soils and increase the planting of hedgerows and trees, and by implementing an ambitious new strategy for the restoration of our peatlands, we can drive carbon back into the ground.

Tom Fyans

Deputy chief executive, Campaign to Protect Rural England

• Leading the way in becoming a net zero-carbon country would be a massive challenge, but there is a strong social case for doing so, as well as a practical, moral and strategic one (Editorial, 3 May). It affords us a timely opportunity to bring the country together in an act of national social renewal, by challenging individuals and communities to work together, share good practice and even compete with each other to become the greenest business, town or village in the land. Britain leading the world in carbon reduction could be a way to redefine patriotism for this century and move us on from all those outdated second world war references so beloved of rightwing politicians.

Richard Aldwinckle

London

• Extinction Rebellion rightly warns of looming catastrophe. Greta Thunberg rightly suggests panic is an appropriate response. Deciding on the best action is now critical. But here’s the problem: most people think reducing CO 2 emissions is the “solution” to climate change. The reality is that we also need to start work: removing the trillion tons of CO 2 that’s already overheating the planet; and refreezing the Arctic before meltdown becomes irreversible. The increase of CO 2 in the atmosphere and the retreat of Arctic sea ice must be halted within a few years. Further intervention for two or three decades can restore the climate norms our grandparents enjoyed.

The Foundation for Climate Restoration has been promoting an intervention strategy. It was founded last year by innovator and philanthropist Peter Fiekowsky, and has identified a number of safe and affordable intervention techniques for CO 2 removal and sea-ice restoration. Past norms could be restored by 2050 at a cost of less than a thousandth of global GDP per year. The foundation is seeking investment for the development of an initial set of technologies, some of which may eventually pay for themselves. But government support is also needed: for changing agricultural practice to put more carbon in the soil; for promoting algae in our oceans to sequester carbon while restoring fisheries; and for deploying cloud cooling technology and other techniques to refreeze the Arctic.

John Nissen

Chair of the Arctic Methane Emergency Group, a partner of the Foundation for Climate Restoration

• Most human activities are dependent on the use of energy, whether from fossil fuels or renewable sources. Cutting carbon emissions provides a dangerously false impression of progress towards any target – for 2030, 2040 or 2050 - aimed at reducing climate change. As the figures published daily on the Guardian weather page show, the concentration of emissions in the atmosphere is rising inexorably. That is the cause of rising temperatures.

It is only when zero global emissions have been achieved that the world can begin to benefit from their reduction. In the years that it will take to arrive at that level, the situation will be graver as, meanwhile, emissions are being added to the existing concentration. It will require stopping using any fossil fuels, whether for heating and hot water, petrol, diesel and most electricity-powered car use, train travel, second homes abroad, air travel, carnivorous diets, long distance freight – and large families.

Only governments can make this mandatory. They have no other option. Are we too selfish to forgo our preferred lifestyles even though that will mean our children and grandchildren will face Armageddon?

Dr Mayer Hillman

London

• Join the debate – email guardian.letters@theguardian.com

• Read more Guardian letters – click here to visit gu.com/letters

• Do you have a photo you’d like to share with Guardian readers? Click here to upload it and we’ll publish the best submissions in the letters spread of our print edition