An illustration from The Sonoran Desert Museum.
The cacti scatter their seeds across the desert. Millions of these tiny seeds are released and land on the hot dry ground. In the vast majority of cases the seed simply dies, it fails to penetrate the hard-baked soil and gets burnt by unbearable heat of the direct sunlight. The sun is absolutely essential for life on earth, but un-mediated exposure to its rays is unbearable by any living thing.
For a cactus seed to survive, to find a safe place to germinate and bear fruit - it requires protection. Most of the cacti which actually live, do so because they fall under the shade of a tree. The tree breaks up the ground creating places for seeds to settle, but most importantly provides shade from the Sun's destructive rays. Under the shadow of the wings of the tree, the seed is not destroyed, but can live. The tree provides a safe place for the seed, and a canopy or covering ensuring its survival. Strong, healthy desert Cacti often appear as in the photo above - springing up from within the circle of protection of a tree.
But what does the cacti provide for the tree in response? What symbiotic arrangement do they have which feeds-back some advantage to the tree? The amazing answer is that while the Cacti requires the tree to live, this arrangement kills the tree. The tree lays down its life to protect the cactus from the Sun. Many a vibrant cactus springs from the dead wood of the tree that died to give it life.
Golgotha, Calvary, The Cross. The burning rays of the Holiness of God - which while they give life to the world are unbearable if unmediated and threaten to destroy us. Yet, in Jesus Christ, God has provided a safe place for us to settle, to nestle, to live and be fruitful. In the shadow of his wings there is safety, security, and life - for ever. But what do we provide Christ with, as our part of this bargain? What is our half of this symbiotic arrangement? The answer is that we kill him. Providing the safety we need to have life, required that he be nailed to a dead piece of wood, gasping for moisture as he died beneath the desert sun.
1 Peter 2:24 He himself bore our sins in his body on the cross, so that we might die to sins and live for righteousness.