diff --git a/DESCRIPTION b/DESCRIPTION
index 7d9309b..bd2fdf8 100644
--- a/DESCRIPTION
+++ b/DESCRIPTION
@@ -24,7 +24,6 @@ Imports:
     ggpattern,
     ggplot2 (>= 3.4.0),
     ggraph,
-    ggstream,
     ggvoronoi,
     grDevices,
     igraph,
@@ -41,6 +40,7 @@ Imports:
 Suggests:
     deldir,
     elevatr,
+    ggstream,
   	MetBrewer,
   	metR,
   	particles,
diff --git a/R/streams.R b/R/streams.R
index f5a2a9f..a743a3e 100644
--- a/R/streams.R
+++ b/R/streams.R
@@ -17,42 +17,46 @@ streams <- function(bg_col = "white",
                                  "#94346E", "#6F4070"),
                     type = "right",
                     s = 1234) {
-  if (!(type %in% c("up", "down", "left", "right"))) {
-    stop('Type must be one of "up", "down", "left", or "right"')
+  if (!requireNamespace("ggstream")) {
+    stop("Please install {ggstream} to use this function.")
+  } else {
+    if (!(type %in% c("up", "down", "left", "right"))) {
+      stop('Type must be one of "up", "down", "left", or "right"')
+    }
+    set.seed(s)
+    # make data
+    n <- length(fill_col)
+    df <- purrr::map_dfr(.x = 1:n,
+                         .f = ~{
+                           x <- 1:sample(1:10, 1)
+                           tibble::tibble(x = x + sample(1:25, 1)) |>
+                             dplyr::mutate(y = sample(1:10, length(x), replace = TRUE),
+                                           z = as.character(.x))
+                         })
+    # plot
+    p <- ggplot2::ggplot(data = df,
+                         mapping = ggplot2::aes(x = .data$x,
+                                                y = .data$y,
+                                                fill = .data$z)) +
+      ggstream::geom_stream(color = line_col,
+                            sorting = "onset") +
+      ggplot2::scale_fill_manual(values = fill_col) +
+      ggplot2::theme_void() +
+      ggplot2::theme(legend.position = "none",
+                     panel.background = ggplot2::element_rect(fill = bg_col,
+                                                              colour = bg_col),
+                     plot.background = ggplot2::element_rect(fill = bg_col,
+                                                             colour = bg_col))
+    #rotate
+    if (type == "up") {
+      p <- p + coord_flip(expand = FALSE)
+    } else if (type == "left") {
+      p <- p + coord_cartesian(expand = FALSE) + scale_x_reverse()
+    } else if (type == "down") {
+      p <- p + coord_flip(expand = FALSE) + scale_x_reverse()
+    } else if (type == "right") {
+      p <- p + coord_cartesian(expand = FALSE)
+    }
+    return(p)
   }
-  set.seed(s)
-  # make data
-  n <- length(fill_col)
-  df <- purrr::map_dfr(.x = 1:n,
-                       .f = ~{
-                         x <- 1:sample(1:10, 1)
-                         tibble::tibble(x = x + sample(1:25, 1)) |>
-                         dplyr::mutate(y = sample(1:10, length(x), replace = TRUE),
-                                       z = as.character(.x))
-                       })
-  # plot
-  p <- ggplot2::ggplot(data = df,
-                       mapping = ggplot2::aes(x = .data$x,
-                                              y = .data$y,
-                                              fill = .data$z)) +
-    ggstream::geom_stream(color = line_col,
-                          sorting = "onset") +
-    ggplot2::scale_fill_manual(values = fill_col) +
-    ggplot2::theme_void() +
-    ggplot2::theme(legend.position = "none",
-                   panel.background = ggplot2::element_rect(fill = bg_col,
-                                                            colour = bg_col),
-                   plot.background = ggplot2::element_rect(fill = bg_col,
-                                                           colour = bg_col))
-  #rotate
-  if (type == "up") {
-    p <- p + coord_flip(expand = FALSE)
-  } else if (type == "left") {
-    p <- p + coord_cartesian(expand = FALSE) + scale_x_reverse()
-  } else if (type == "down") {
-    p <- p + coord_flip(expand = FALSE) + scale_x_reverse()
-  } else if (type == "right") {
-    p <- p + coord_cartesian(expand = FALSE)
-  }
-  return(p)
 }