diff --git a/API.txt b/API.txt
index a7a5f62..fd234ed 100644
--- a/API.txt
+++ b/API.txt
@@ -112,9 +112,9 @@ biome = {
 	depth_max = num,	-- If the object spawns on top of a water source, the
 						-- water must be at most this deep.  Defaults to 1.
 	min_elevation = num, -- Surface must be at this altitude or higher to
-						-- spawn at all.  Defaults to -31000...
-	max_elevation = num, -- ...but must be no higher than this altitude.
-						-- Defaults to +31000.
+						 -- spawn at all.  Defaults to -16 meters.
+	max_elevation = num, -- Surface must be no higher than this altitude.
+						 -- Defaults to +48.
 	near_nodes = {table}, -- List of nodes that must be somewhere in the
 						-- vicinity in order for the plant to spawn. Can also
 						-- be a string with a single node name.  If not
@@ -270,8 +270,8 @@ biome = {
 	depth = num,		-- How deep/thick of a layer the spawned-on node must
 						-- be.  Typically used for water.
 	min_elevation = num, -- Minimum elevation in meters/nodes.  Defaults to
-						-- -31000 (unlimited).
-	max_elevation = num, -- Max elevation.  Defaults to +31000 (unlimited).
+						-- -16 meters.
+	max_elevation = num, -- Max elevation.  Defaults to +48m.
 	near_nodes = {table}, -- what nodes must be in the general vicinity of the
 						-- object being spawned.
 	near_nodes_size = num, -- how wide of a search area to look for the nodes
diff --git a/init.lua b/init.lua
index 2b000ff..684b740 100644
--- a/init.lua
+++ b/init.lua
@@ -33,6 +33,10 @@ biome_lib.actionslist_no_aircheck = {}
 biome_lib.surfaceslist_aircheck = {}
 biome_lib.surfaceslist_no_aircheck = {}
 
+-- the mapgen rarely creates useful surfaces outside this range, but mods can
+-- still specify a wider range if needed.
+biome_lib.mapgen_elevation_limit = { ["min"] = -16, ["max"] = 48 } 
+
 biome_lib.modpath = minetest.get_modpath("biome_lib")
 
 local function tableize(s)
@@ -153,8 +157,8 @@ end
 
 function biome_lib:set_defaults(biome)
 	biome.seed_diff = biome.seed_diff or 0
-	biome.min_elevation = biome.min_elevation or -31000
-	biome.max_elevation = biome.max_elevation or 31000
+	biome.min_elevation = biome.min_elevation or biome_lib.mapgen_elevation_limit.min
+	biome.max_elevation = biome.max_elevation or biome_lib.mapgen_elevation_limit.max
 	biome.temp_min = biome.temp_min or 1
 	biome.temp_max = biome.temp_max or -1
 	biome.humidity_min = biome.humidity_min or 1
@@ -206,6 +210,9 @@ function biome_lib:register_generate_plant(biomedef, nodes_or_function_or_model)
 		biome_lib.dbg("Warning: Registered function call using deprecated string method: "..dump(nodes_or_function_or_model), 2)
 	end
 
+	biome_lib.mapgen_elevation_limit.min = math.min(biomedef.min_elevation or 0, biome_lib.mapgen_elevation_limit.min)
+	biome_lib.mapgen_elevation_limit.max = math.max(biomedef.max_elevation or 0, biome_lib.mapgen_elevation_limit.max)
+
 	if biomedef.check_air == false then 
 		biome_lib.dbg("Register no-air-check mapgen hook: "..dump(nodes_or_function_or_model), 3)
 		biome_lib.actionslist_no_aircheck[#biome_lib.actionslist_no_aircheck + 1] = { biomedef, nodes_or_function_or_model }
@@ -859,6 +866,8 @@ end
 minetest.after(0, function()
 	biome_lib.dbg("Registered a total of "..(#biome_lib.surfaceslist_aircheck)+(#biome_lib.surfaceslist_no_aircheck).." surface types to be evaluated, spread", 0)
 	biome_lib.dbg("across "..#biome_lib.actionslist_aircheck.." actions with air-checking and "..#biome_lib.actionslist_no_aircheck.." actions without.", 0)
+	biome_lib.dbg("within an elevation range of "..biome_lib.mapgen_elevation_limit.min.." and "..biome_lib.mapgen_elevation_limit.max.." meters.", 0)
+
 end)
 
 biome_lib.dbg("[Biome Lib] Loaded", 0)
diff --git a/search_functions.lua b/search_functions.lua
index 118e121..85772fc 100644
--- a/search_functions.lua
+++ b/search_functions.lua
@@ -57,18 +57,26 @@ end
 
 minetest.register_on_generated(function(minp, maxp, blockseed)
 	local timestamp = minetest.get_us_time()
-	for x = 0, 4 do
-		local minx = minp.x + x*16
-		for y = 0, 4 do
-			local miny = minp.y + y*16
-			for z = 0, 4 do
-				local minz = minp.z + z*16
+	for y = 0, 4 do
+		local miny = minp.y + y*16
 
-				local bmin = {x=minx, y=miny, z=minz}
-				local bmax = {x=minx + 15, y=miny + 15, z=minz + 15}
-				biome_lib.block_log[#biome_lib.block_log + 1] = { bmin, bmax, true, timestamp }
-				biome_lib.block_log[#biome_lib.block_log + 1] = { bmin, bmax, false, timestamp }
+		if miny >= biome_lib.mapgen_elevation_limit.min
+		  and (miny + 15) <= biome_lib.mapgen_elevation_limit.max then
+
+			for x = 0, 4 do
+				local minx = minp.x + x*16
+
+				for z = 0, 4 do
+					local minz = minp.z + z*16
+
+					local bmin = {x=minx, y=miny, z=minz}
+					local bmax = {x=minx + 15, y=miny + 15, z=minz + 15}
+					biome_lib.block_log[#biome_lib.block_log + 1] = { bmin, bmax, true, timestamp }
+					biome_lib.block_log[#biome_lib.block_log + 1] = { bmin, bmax, false, timestamp }
+				end
 			end
+		else
+			biome_lib.dbg("Did not enqueue mapblocks at elevation "..miny.."m, they're out of range of any generate_plant() calls.", 4)
 		end
 	end
 	biome_lib.run_block_recheck_list = true