Why are there are so many crime novels, crosswords and Sudoku puzzles in the world? The human animal clearly loves a good mystery, or a puzzle to solve. Working from clues to solutions is not everybody's idea of fun, but for many, this deductive way of looking at the world is satisfying, addictive and infectious. I have been infected for at least 20 years – for me, it's a chronic condition.
However, unlike most characters – real and fictional – that have revelled in this pastime over the years, my passion for deduction has been focused outdoors. Sherlock Holmes may have felt the mist of the moor under his deerstalker on occasion, but he had a distinct preference for indoor clues over outdoor ones. While I doff my Panama in Mr Holmes' general direction, I venture to suggest that he would have done well to spend more time looking at the clues in nature and less time peering at cigar ash through a magnifying glass.
Within the world of natural clues, the field that fills most of my working hours is the rare art of natural navigation. I have spent much of the past two decades studying, practising, teaching and writing books about clues to direction in nature. My latest book, The Walker's Guide to Outdoor Clues & Signs, is the one I like to think Sherlock would read while on holiday. But to see if this game is for you, I recommend that you attempt to cross a city park like an explorer.
Many of the skills explorers have depended upon can be used practically over very short distances, even in the middle of cities. And I'm talking about real explorers here. The old type; the ones who saw stuff without names, let alone names that can be found on Google Earth.
If there is a fundamental skill that separates the successful expedition from one that ends ignominiously, it is effective navigation. In essence, if you continue in a roughly straight line in the direction you want to head, then, avoiding pitfalls, you will succeed in reaching your goal.
Use the sun if it is out. It will rise close to the east most of the year and set close to west most of the year (well south of both in winter and north of both in midsummer, but we're getting ahead of ourselves). To keep things simple set off in the middle of a sunny day, as this is when the sun is due south and you can use this as your first dependable compass.
If you are on the edge of a park, you should be able to find plenty of satellite dishes on roofs, they will point close to south-east in the UK. Now, check the conventional TV aerials and work out which way they are pointing and see if there is a dependable trend. Next, look up and make a mental note of which way the clouds are moving. Using clouds to navigate sounds too woolly to be practical, but I've crossed cities and jungles with the help of clouds alone. Last week, I became disorientated in the Kielder Forest, and peered through a break in the tree canopy at the clouds passing overhead. I knew they were flowing from west to east that day and that was the direction I needed to head.
Now, make your way into the park and look at any trees you find. There are 19 different ways you can use trees to navigate, but there are two good ones to get started with. There will be more tree – by which I mean a greater number of slightly bigger branches – on the southern side of most trees. The tops of trees, even in cities, will often show the effects of having been combed over by the wind. Since most strong winds come from the south-west, we find the tops of trees brushed over ever so slightly towards the north-east. This effect is dramatic in exposed locations and subtle in cities, but can be spotted in the tops of trees all over the world.
The next thing to do is look down. Look at the grasses and mud near your feet. Explorers need to take a professional interest in the routes of others. If someone has gone before you, and that is quite likely in a park, there will be clues to what they got up to. With a lot of practice, you can tell the height, weight, sex, speed and mental state of a person from their tracks in the ground. But to start with, just try seeing if you can spot the most common routes across the grass.
Now you are ready to study how the plants can help with finding tracks. Some plants can handle being walked over and some can't. Plantains do better than most plants on commonly walked routes and they are easy to spot – those big weed-like leaves you see among the grass. If you look carefully, you will spot that they are more common along some lines than others. These plants reveal paths that are easy to spot when you know how, but which few people notice.
Every plant is a clue to something, and most can help with finding direction. Notice how you get a lot of different wildflowers on a south-facing bank, but far fewer on a north-facing one. Now get down really low – checking for canine clues first, perhaps – and look at some daises from the side. Notice how the stalks of the taller daisies curve a little towards the south on average.
Now look at the trees again. Mature trees have survived a long time and this means they must be suited to their environment. Turn this logic around and hopefully you can see that trees can all be used as a really good clue to the surrounding area. London planes earned that name because they are one of the few trees to tolerate both city pollution and crushed roots; they will now be found in cities all over the world. But the trees that give clues about water are a bit more interesting. Beech trees hate ground that gets waterlogged and so are a sign of dry ground, but willows and alders are a sign you are getting close to water. If you are lucky enough to be in a park by a river or lake, notice how the trees change dramatically close to the water. The trees are mapping the land for you, and this is a trick that has saved the lives of countless thirsty explorers.
If at any stage you feel a mild terror that you are perhaps lost in a great wilderness, then there is plant that can calm your nerves. Stinging nettles don't grow anywhere; they need a lot of phosphate in the soil. The way humans live makes the soil richer in phosphates. Put these two pieces of information together and you can see that stinging nettles are a clue to nearby human habitation.
Press on, using the sun, clouds and trees to hold your course, and you will reach the far side of the park. All it remains to do is to remove your pith helmet and prepare your report for the Royal Geographical Society.
'The Walker's Guide to Outdoor Clues & Signs' by Tristan Gooley is published by Sceptre (Hardback, £20). For more information, see naturalnavigator.com