To people, salt is a kitchen staple. But to crops, too much of it can be devastating.

Across coastal regions and irrigated agricultural land, salt is accumulating in soils, making it harder for plants to absorb water and reducing harvests. Scientists estimate that around half of the world’s irrigated farmland is now affected by salinity to some degree.

The problem is only expected to grow. Rising sea levels can push saltwater into coastal farmland, while changing rainfall patterns and more frequent droughts are increasing reliance on irrigation. Poor-quality irrigation water and the overuse of fertilisers can worsen the problem, leaving salts behind in the soil year after year.

This is an issue because the global population is expected to approach 10 billion by the middle of the century, while demand for food continues to rise. Finding ways to grow crops in increasingly difficult conditions is becoming one of agriculture’s biggest challenges.

But plants are not passive victims. Beneath the surface, their roots are engaged in a constant battle with their environment. They sense danger, adapt their growth and deploy sophisticated strategies to survive.

Underground intelligence network

Roots do far more than anchor plants in the ground. They are the plant’s frontline, constantly gathering information about the soil around them. Every day, roots assess water availability, nutrient levels and environmental threats. When salt levels begin to rise, they are the first part of the plant to detect the change.

For plants, excess salt creates a double challenge. First, it makes it harder to draw water from the soil, almost as if the plant is trying to drink through a blocked straw. Second, sodium can build up inside tissues, damaging cells and interfering with essential biological processes.

Roots can detect these changes remarkably quickly. As salt concentrations increase, cells in the root begin sending warning signals through the plant. These signals trigger a cascade of responses, including shifts in hormone levels and the activation of emergency survival mechanisms designed to protect growth.

One of the most remarkable things about roots is their flexibility. Unlike the branches above ground, roots can continually reshape themselves in response to changing conditions. Faced with salty soil, they may alter how deeply they grow, how many side branches they produce and even the direction they travel.

In effect, roots can steer themselves away from trouble. Research has shown that plants can bend roots away from highly saline patches of soil while continuing to search for water and nutrients elsewhere. Growth may slow in certain areas, helping the plant avoid pushing vulnerable new tissues into harmful conditions.

This hidden reshaping of the root system can make a difference to the chances of survival. By avoiding the saltiest parts of the soil, plants can reduce the amount of sodium they absorb while continuing to access the resources they need.

At the same time, roots are working to control any salt that does enter the plant. Excess sodium is dangerous because it can damage proteins and cell membranes. To prevent this, root cells actively move sodium into storage compartments where it can do less harm, or pump it back into the surrounding soil.

The result is a carefully managed balancing act that helps protect the more sensitive tissues above ground.

Can plants ‘remember’ stress?

Perhaps the most surprising area of research is the idea that plants may be able to learn from experience. Scientists are increasingly finding evidence that previous exposure to environmental stress can influence how plants respond in the future. In crops such as rice, for example, plants that have encountered salt before can sometimes cope better when exposed to it again.

Rather than involving memory in the human sense, these experiences appear to leave lasting chemical marks on DNA and associated structures within cells. These marks can influence which genes are switched on or off when stress returns, allowing plants to respond more quickly or effectively.

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Read more: How plants are able to remember stress without a brain

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Similar effects have been observed in responses to heat and drought stress. It suggests that plants may possess a surprisingly sophisticated ability to prepare for future challenges.

Some studies even suggest that aspects of these stress responses could be passed to the next generation, potentially helping offspring cope better with harsh environments. While many questions remain unanswered, the possibility that plants can retain and pass on information about past stresses is opening up an exciting new area of research.

But what does this mean for future food supplies? As salt levels in soil increase, crops face mounting pressure. Salinity can stunt growth, reduce yields and leave plants less able to cope with other challenges such as drought and extreme heat. In reality, these stresses often arrive together. That’s why understanding roots has become such an important scientific priority.

The better researchers understand how roots detect, avoid and tolerate salt, the better equipped breeders will be to develop crops that can thrive in difficult conditions. By identifying the root traits that help plants survive saline environments, scientists may be able to breed or engineer varieties capable of maintaining yields on land that would otherwise become less productive.

Much of this battle is invisible, unfolding centimetres below our feet. But the decisions that roots make underground could have profound consequences above ground. In a future where climate change is making agriculture increasingly unpredictable, the key to protecting food supplies may lie in understanding how plants wage their quiet war against salt.

Amber Williams receives funding from UKRI.

Seventy years ago, Britain confronted a dilemma. It wanted to remain a leading military power but no longer had the economic resources to sustain all the conventional capabilities it had inherited from the second world war.

The solution proposed in the 1957 Sandys defence white paper was technological. Guided missiles, Duncan Sandys argued, were transforming warfare so fundamentally that many traditional capabilities, including some crewed combat aircraft, would become obsolete.

In other words, by embracing this technological revolution, Britain could achieve defence on the cheap. Britain’s new Defence Investment Plan (DIP) reflects a similar strategic instinct. The technologies may have changed but the underlying dilemma has not.

Announcing the DIP in the House of Commons, Dan Jarvis, the defence secretary, said the UK would be making its “largest ever investment in drone warfare: £5 billion for strike, protector and surveillance drones across the Royal Navy, the Army and the Royal Air Force.”

Here are some of the key technologies discussed in the Dip.

Drone ships

At least a quarter of the £5 billion announced for drone warfare is going towards a “hybrid fleet,” a fundamental re-imagining of the Royal Navy. The UK’s sole ballistic missile defence capability – the Type 45 destroyers – will no longer be replaced by a like-for-like. Instead, a network of Crewed Combat Vessels (CCVs) will act as control hubs for specialised, uncrewed boats.

These would include Type 91 missile barges, Type 92 and Type 93 anti-submarine and underwater surveillance platforms, and Type 94 radar vessels. In principle, distributing the sense, decide and strike functions across the navy offers several advantages.

It could ease chronic personnel shortages by reducing crew requirements, extend radar and sonar coverage over a wider area, and make the fleet more resilient by dispersing combat power rather than concentrating it in a handful of expensive warships.

Uncrewed vessels could also be rearmed or maintained independently and without the design constraints of supporting sailors at sea. However, the challenges are significant.

The DIP envisages this concept becoming proven and operational before the Type 45 retires in the mid-2030s, despite the fact that resilient communications and electronic warfare protection for autonomous warships remain immature.

Nor is Ukraine’s use of naval drones a straightforward template. The Royal Navy’s principal tasks – particularly anti-submarine warfare in the High North and North Atlantic – are far more demanding than Ukraine’s use of maritime drones in the Black Sea.

While experiments such as using RFA Lyme Bay as a mothership for autonomous mine countermeasures (including drone minesweepers) are encouraging, retiring Britain’s only ballistic missile defence destroyers before the wider architecture has been proven would entail significant operational risk.

AI targeting network

The army’s Project Asgard illustrates the same technological philosophy in a different domain. Asgard aims to transform how – and how quickly – the army identifies and strikes targets, by linking sensors, armoured vehicles, drones and long-range weapons into a single, AI-enabled targeting network.

First trialled in 2025, Asgard is now receiving £370 million to develop an operational capability, reflecting the Army’s ambition to achieve a tenfold increase in combat power primarily through automation rather than expanded forces.

This idea has an important intellectual history. During the 1990s, the United States championed the concept of network-centric warfare: the proposition that superior information sharing would enable smaller, more agile forces to defeat numerically superior opponents. But Britain was soon concerned about the affordability and technological challenge of creating such highly connected forces, adopting in its place a lighter version: network-enabled capabilities.

The DIP suggests that the government now believes the technology is catching up with the theory. But old weaknesses remain. Networks only work if they survive. Communications can be jammed, satellites disrupted and software attacked, and Russia has the electronic warfare capabilities that could, without adequate safeguards, do all three.

‘Loyal wingmen’

It is also the case that what has worked at smaller levels now needs to be scaled across Nato. If it works, Project Asgard would provide Nato land forces with the ability to control long-range weapons of their own, reducing their reliance on air forces which will need to focus on supressing and destroying enemy air defences.

That task is motivating the DIP’s investment in Collaborative Combat Aircraft (CCAs) – uncrewed platforms that will fly alongside the RAF’s Typhoons and F-35s.

These “loyal wingmen” drones would support crewed aircraft by acting as scouts, decoys, absorbing enemy fire or jamming enemy radars. They could be controlled by the pilot of the combat jet, or work autonomously.

Systems such as the MQ-28 Ghost Bat are at an early stage of development. To be militarily useful CCAs must combine long range, high speed, low observability, resilient data links and meaningful payloads, requirements that quickly approach the complexity, and potentially the cost, of the crewed aircraft they are intended to complement.

Will it be cheaper?

Against these challenges, the government’s headline commitment of £5 billion on these systems therefore seems more like a down payment than the full mortgage. Spread across four years, three armed services and an exceptionally diverse range of programmes, it is less transformative than some may believe, and certainly not on the timelines some think are necessary as tensions continue with Russia.

The unit costs of what will be specialist equipment may remain prohibitively expensive. Take the hybrid Navy as an example. The autonomous systems in question require resilient communications, sophisticated sensors, electronic warfare protection and high engineering reliability, meaning the combined cost of CCVs and their uncrewed flotillas could approach that of the destroyers they replace.

Even if the funding can be found – and there are good reasons to question whether it can – Britain must still demonstrate that its defence industry can deliver this technology-intensive force. Expanding military output requires far more than larger budgets: it demands additional factory capacity, skilled workers, shipbuilding infrastructure and resilient supply chains. This is particularly true for autonomous systems whose military value depends on being produced, sustained and replaced at scale.

The DIP rests on three assumptions: that autonomous systems mature quickly, prove affordable and can be produced at scale. The Sandys Review rightly foresaw the missile age but underestimated the staying power of conventional forces; new technologies reshape warfare but they rarely replace its enduring fundamentals.

If Britain is to bet on autonomy, therefore, it also needs the spending profile to make that bet credible. After all, the most important judgement on the DIP will not be that of future historians, but of the occupant of the Kremlin today.

Arun Dawson is affiliated with the Royal United Services Institute.