Archive | August 2016

First Rain Part II: a Moveable Feast

I am sitting outside in the early morning of a cloudy day, after a long, soaking rain that lasted through the night. Swarms of termites hover over the ground and crawl along the wall.  A gecko, normally strictly nocturnal,  is dashing from the cover of a window frame  to  take advantage of this sudden abundance. It seems to know they will be gone soon and this rich feast is too much to ignore, even at the risk of being eaten himself.

Termites are social insects with a caste system. Each colony will have a king and a queen. The queen grows a huge abdomen and pumps out thousands of eggs. The eggs hatch and are divided into workers, soldiers and winged reproductives called alates. The alates have been waiting for the rain.

Termites are essential members of the desert ecosystem. Living underground by the millions, they take the energy and nutrients from dead and decaying vegetable material and redistribute it down into the soil. They do not have a waterproof skin, so they remain underground or build inverted tunnels of chewed cellulose and saliva along the surface of dead grass, sticks and hard surfaces like cement. In this way they search for food without exposing themselves to the dry air.  But after a rain, they take advantage of the humidity to spread farther and faster than tunneling would ever allow. Great swarms of alates take to the air, hoping to find a mate and settle on the ground, look for some wood to chew into and start a new colony. Most don’t make it.

The mating swarm of termites is a rich source of food for many desert animals. Bats, dragonflies and birds snatch them from the air. On the ground they are gobbled up by toads, lizards, snakes, mice, skunks, coatis, more birds and a variety of invertebrates such as ant lions, scorpions and spiders. And the timing couldn’t be more perfect.

This sudden burst of available protein and energy will fuel the mad dash that high temperatures, and abundant moisture and sunlight will bring to the desert. For it won’t be long before the ponds dry, the soil bakes hard again, and most life will shut down or go underground until the rains come again, many months from now.

 

 

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The Desert Responds to its First Rain: Part 1

The thunderstorm came in just after sunset. Temporarily blinded by a nearby bolt of lightning, I can feel the thunder in my chest. Quickly the storm moves on and the air is filled with a new sound: the calling of thousands of toads. I am standing outside a room at the Posada, with Matt and Richard, two American conservationists spending the night, and sharing their beer with me.

We wander down to a newly-created pond, drawn by the mating calls of Couch’s spadefoot toads, Scaphiopus couchii . Already they are pairing up, the males embracing the females from behind. Soon eggs will be laid, fertilised and left to fend for themselves in a pond which will completely dry up in less than two weeks.

I remember the calls of frogs and toads from my childhood in Northern Ontario. Each species would have its own season, throughout the spring and summer months, and I could hear the calls from my bedroom window.

So imagine my surprise when the very next night, I went down to the pond to listen to the toads and was met with silence. Northern frogs time their mating by temperature and day-length, and call for weeks before all are mated. But in the desert, the ponds dry up, and so the tadpoles have a short time to grow and transform into adult toads.

The mating was over that first night, and already the eggs were hatching into tiny tadpoles. The adult toads have a few days to feed before the ground starts to harden, and they burrow in again to await the next rains.

Nacapule Canyon

San Carlos is located near the southern edge of the Sonoran Desert, but it hasn’t always been desert. During periods of a wetter climate, this area was a part of the Tropical Deciduous Forest. As the climate dried again, the Tropical Deciduous Forest retreated to the south, and was replaced with the desert vegetation we see today. There remain, however, a few places where the tropical forest species survive.

The Nacapule Canyon is one such place. A deep, narrow gap carved into in the surrounding hills, the Nacapule Canyon is shaded much of the day, which reduces evaporation. Much of the surrounding rock is porous volcanic ash, which absorbs the rain and slowly releases it to the bottom of the canyon. The result is an oasis, where tropical deciduous forest trees and shrubs can survive, completely surrounded by desert.

The entrance to the canyon is a broad trail, an easy hike up the arroyo. The walls of the canyon are made up of layers of red, yellow and grey rock twisted and carved into weird and beautiful patterns. A short zipline crosses overhead, accessible by climbing a short, steep trail. The trail follows the arroyo, sometimes running alongside, where the arroyo is filled with boulders. As you follow the gentle slope upwards, you come to the tree from which the canyon is named, a Canyon or Macapule Fig. There was an even larger specimen nearby, but it was wiped out by the terrible rains of a hurricane.

The canyon splits here, one branch following the edge of a permanent stream, to the right, the other, a dry arroyo straight ahead. Neither branch goes very far, so there is time to explore both. The right fork becomes thick with vegetation as it follows a small permanent stream and wanders through a thicket of palm trees. After the palm trees, the way gets steep, and there is a small cave to explore, or to travel through as you start to climb. Climbing higher brings you to a larger cave, some small ponds and eventually you come out on top, and the trail descends to the desert to the north of the canyon. Rather than descend, if you got this far, you can turn around and head back to the fork

Following the second fork, brings you to a dry waterfall below a series of plunge-pools. There is a rope ladder on the right which brings you to the top of the falls. From here you can see more pools, glistening black in the sunlight. There is even a Nacapule Canyon leopard frog here, if you can spot it. Can you imagine a frog in such an isolated place surrounded by desert?

The Nacapule Canyon is a jewel in the desert, a place to explore, or just to spend a moment of peace.

Summer Monsoon

It’s night, about an hour after sunset. The fluffy clouds of the afternoon have congealed into a solid mass of blackness, blocking out the stars. Yet all is not dark. There are flashes beyond the hills, several every second, coming more frequently as the minutes pass.

While the sun was up the humidity was quite bearable. Now that the sun has set, the air has become so saturated that the sweat glistens on my skin and soaks my clothes, refusing to evaporate. This is the summer monsoon.

When we hear the word “monsoon” we may think of a tropical forest, of swollen, muddy rivers, of flooded roads, of hot, humid nights alive with the buzzing of insects and the drumming of rain on tin roofs. In some parts of the world, that is a pretty accurate picture. But, despite what many people from the American Southwest are led to believe,  monsoon is not rain. You hear up in Tucson, “We had a real monsoon last night, I’ll tell ya.” They get that from the phrase “monsoon rain”. The fact the word “rain” is in the phrase should tell you that monsoon is not a type of rain. You don’t hear people talk of “thunderstorm rain” or “heavy shower rain”; that would be redundant.

So what is monsoon then? The word comes from the  Arabic, mawsim, meaning “season”. The monsoon is a seasonal wind-driven weather pattern, which brings dry weather during the winter, and wet weather in the summer. The Indian sub-continent and SE Asia all the way to N Australia are all affected by this weather pattern, as is West Africa and the W coasts of the Americas.

This seasonal shift is what gives it the name monsoon, but the wind pattern is nothing more than a sea breeze on a very large scale. Here in Sonora, the desert heats up in the summer faster than the water from the Gulf of California. The hot, desert air rises, leaving low pressure behind, which is filled in by the cooler air from the sea. As this cooler (not exactly cold), humid air moves inland it is pushed upward over local mountain ranges. As the air rises, two things happen. The air becomes over-saturated with moisture and forms tall clouds with growing tops. And the ascending clouds generate static electricity. This build-up becomes too much for the cloud, and a thunderstorm is the result.

Even the hardiest desert shrub needs rain. All through the winter and spring the desert has become drier and drier. The hill-sides are rock and gravel, with a sparse cover of bunches of sere, grey twigs, and the occasional cactus.standing in green defiance. The arrival of the monsoon has been a cruel joke to this tough vegetation. Hot humid air gives no relief and the nightly show of distant lightning does nothing to quench a desperate thirst.

As the monsoon progresses, the storms have grown in size and approached a little closer every night. Some nights they are close enough to hear the thunder (typically less than about 11 miles or about 18 km), and we may even get a spatter of raindrops that glue the dust to the windshield on my pickup without being quite enough to join together and wash the dust away. So we wait. It will come eventually. It must.

And it finally does. Lightning blindly stabs the ground with its crooked spear, shaking the heavens and the earth with great booms of thunder that roll around the hills, blending one with the next in a continuous rumble like the march of an army of giants. The still, moist air is suddenly pushed aside by a strong breeze and you can hear the rain approach. It comes as a wall, pouring from the sky in a solid mass of water, momentarily almost drowning out the sound of thunder.

Soon both thunder and rain abate slightly, and during the flashes of light, one can see that the road has been turned into a creek, the middle washing away down the street, leaving a deep, stony gash where a dirt road used to be. Nothing can be done about it, so we watch the storm and celebrate.